Textile and Leather Review 1 2021

TEXTILE & REVIEW LEATHER

1/2021 Volume 4 Issue 1 2021 textile-leather.com ISSN 2623-6257 (Print) ISSN 2623-6281 (Online)

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Shahid Adeel, Government College University Faisalabad, Department of Chemistry, Pakistan Emriye Perrin Akçakoca Kumbasar, Ege University, Faculty of Engineering, Turkey Tuba Bedez Üte, Ege University, Faculty of Engineering, Turkey Mirela Blaga, Gheorghe Asachi Technical University of Iasi, Faculty of Textiles, Leather and Industrial Management, Romania Patrizia Calefato, University of Bari Aldo Moro, Department of Political Sciences, Italy Andrej Demšar, University of Ljubljana, Faculty of Natural Sciences and Engineering, Slovenia Krste Dimitrovski, University of Ljubljana, Faculty of Natural Sciences and Engineering, Slovenia Ante Gavranović, Economic Analyst, Croatia Ana Marija Grancarić, University of Zagreb, Faculty of Textile Technology, Croatia Huseyin Kadoglu, Ege University, Faculty of Engineering, Turkey Fatma Kalaoglu, Istanbul Technical University, Faculty of Textile Technologies and Design, Turkey Hüseyin Ata Karavana, Ege University, Faculty of Engineering, Turkey Ilda Kazani, Polytechnic University of Tirana, Department of Textile and Fashion, Albania Vladan Končar, Gemtex – Textile Research Laboratory, Ensait, France Stana Kovačević, University of Zagreb, Faculty of Textile Technology, Croatia Aura Mihai, Gheorghe Asachi Technical University of Iasi, Faculty of Textiles, Leather and Industrial Management, Romania Jacek Mlynarek, CTT Group – Textiles, Geosynthetics & Flexibles Materials, Canada Abhijit Mujumdar, Indian Institute of Technology Delhi, India Monika Rom, University of Bielsko-Biala, Institute of Textile Engineering and Polymer Materials, Poland Venkatasubramanian Sivakumar – CSIR – Central Leather Research Institute, Chemical Engineering Department, India Pavla Těšinová, Technical university of Liberec, Faculty of Textile Engineering, Czech Republic Savvas Vassiliadis, Piraeus University of Applied Sciences, Department of Electronics Engineering, Greece

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Textile & Leather Review ‒ ISSN 2623-6257 (Print), ISSN 2623-6281 (Online) UDC 677+675 DOI: https://doi.org/10.31881/TLR Frequency: 4 Times/Year The annual subscription (4 issues).

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TEXTILE & LEATHER REVIEW ISSN 2623-6257 (Print)

ISSN 2623-6281 (Online) CROATIA

VOLUME 4

ISSUE 1

2021

p. 1-60

CONTENT REVIEW 5-22

Antiviral Finishing on Textiles - An Overview Goutam Bar, Debjit Biswas, Shrutirupa Pati, Kavita Chaudhary, Mahadev Bar

ARTICLE 23-29

Assessment of the Carbon Footprint and VOCs Emissions Caused by the Manufacturing Process of the Footwear Industry in Bangladesh Yead Mahmud, Md. Rashed-Ul-Islam, Md. Obaidul Islam, Tanvir Siddike Moin, Khandaker Tanzim Rahman

30-37

Quality Assessment of Shoe Leather Based on the Properties of Strength and Comfort, Collected from Different Footwear and Leather Industries in Bangladesh Md. Delwar Hossain, Forhad Ahammed Bin Azam, Manjushree Chowdhury

38-54

Evaluation of the Bacillus cereus Strain 1-p Protease for the Unhairing of Goatskins during Leather Production Joseph Ondari Nyakundi, Jackson Nyarongi Ombui, Francis Jakim Mulaa, Wycliffe Chisutia Wanyonyi

BAR G, BISWAS D, PATI S, CHAUDHARY K, BAR M. Antiviral Finishing on Textiles … TLR 4 (1) 2021 5-22.

Antiviral Finishing on Textiles - An Overview Goutam BAR1*, Debjit BISWAS1, Shrutirupa PATI1, Kavita CHAUDHARY2, Mahadev BAR3 Department of Textile Design, National Institute of Fashion Technology, Bhubaneswar, India Banasthali Institute of Design, Banasthali University, Banasthali, Rajasthan, India 3 Laboratoire Génie de Production, LGP, Université de Toulouse, INP-ENIT, Tarbes, France *goutam.bar@nift.ac.in 1 2

Review UDC 677.027:578.4 DOI: 10.31881/TLR.2020.17 Received 4 August 2020; Accepted 21 October 2020; Published Online 31 October 2020; Published 2 March 2021

ABSTRACT Antiviral textiles are one of the most promising areas of protective textiles. Antiviral textiles are important in the field of health and hygiene. They become an essential part of our daily-life when a pandemic situation arises. The present paper critically analyses and summarizes various researches of the production of antiviral textiles. Different classes of the virus, how the virus transmits and replicates, various antiviral agents for textiles and their working mechanism, and the application procedure of various synthesized and bio-based antiviral compounds on textiles have been discussed in this paper. Finally, the present paper compares the existing antiviral finishing on textiles in terms of its effectiveness, durability and skin-friendliness and, following that, discusses the possibilities of using antiviral textiles in various sectors.

KEYWORDS Virus, Textiles, Antiviral agent, Antiviral finish, Antiviral textiles

INTRODUCTION History reveals that a virus is the reason behind most of the global pandemics that occurred in the near past, for instance the H3N2 virus behind the influenza pandemic in 1968, the SARS virus behind the 2003 pandemic, the H1N1 virus behind the swine flu pandemic in 2009, the Ebola virus behind the 2014 pandemic and the most recent novel coronavirus behind the 2020 pandemic [1,2]. The World Health Organization (WHO) reported that the diseases caused by viral infections are the second leading cause of human death [3]. Around 250,000 to 500,000 people die every year only due to the influenza virus infection [4]. To prevent or minimize these fatalities, several vaccines are developed by the researchers but these are not sufficient enough to protect human beings from all kinds of viruses. Thus, it is necessary to look for other possible safety measures which can protect us from these deadly viruses, prior to an appropriate vaccine being developed.

Viruses fall in the category of microbes and they are omnipresent [5,6]. NASA researchers have found microbes even at the height of 32 km above the sea level and at the depth of 11 km under the sea level.

It is estimated that all microbes present in the earth are approximately 25-fold the mass of all animals [7].

Microbes have an outer polysaccharide cell wall and a semi-permeable membrane, which protects their inner substrates and preserves their functionality [8,9]. Whenever a microbe finds itself in favourable conditions in terms of temperature and humidity or a host cell, it starts reproducing itself [10]. However, all microbes www.textile-leather.com 5

BAR G, BISWAS D, PATI S, CHAUDHARY K, BAR M. Antiviral Finishing on Textiles … TLR 4 (1) 2021 5-22.

are not the same, they differ from each other in terms of their structure, sizes, habitat etc. In the context of their cellular nature a microbe can be unicellular, multicellular or acellular. Viruses are acellular. In the domain of life, living cells are classified in three categories called Archaea, Bacteria and Eukarya. Most of the microbes fall in the category of Archaea or in the category of Bacteria, but a virus falls in none of these three categories, they are considered to be a grey area between the living and the non-living [11]. Hence, a substrate that provides a perfect protection against a bacterial or other microbial attack, may or may not be useful against a virus.

Whenever we think about human protection, textiles come to our mind first. Textiles protect human beings from extreme weather conditions. With suitable structural design and chemical finishes, textiles can protect a human body from sharp objects, impact thrust, fire accidents, electric shocks etc. [12]. However, textiles, in their parent form (i.e. without any suitable chemical treatment) cannot protect a person from a microbial attack. In fact, textiles are susceptible to microbial growth due to their high moisture retention and surface area [13,14]. The presence of starch, protein and fats in natural fibres makes them more susceptible to a microbial attack. The degeneration of fibre, foul odour, colour change, unwanted stains etc. are the signs of a microbial attack on textiles [7,15,16]. These microbes (microbial attack signs) mainly belong to the bacteria family. Textiles are treated with various synthetic as well as bio-based antibacterial agents in order to protect them and their user from a bacterial attack [8,17,18]. However, a textile fabric treated with antibacterial agents may not act as an antiviral fabric, as the virus and the bacteria are completely different from each other [8,11]. As mentioned earlier, foul odour, colour change, unwanted stains etc. are the signs of bacterial infection on textiles but no such signs are observed when textiles are infected with a virus. Viruses do not replicate or grow on textiles because they require a host cell to be able to do that but viruses are deadlier for the human race than bacteria [19,20].

The world is currently going through a pandemic situation resulting from the novel coronavirus. There are many deadlier viruses present in the world, which are inactive now but can affect the human race at some other time [20]. Hence, it is very much necessary to have a clear concept of antiviral textiles as they act as the first layer of protection against the unknown viruses, before the development of a vaccine or a medicine.

The present paper critically analyses and summarizes various researches on producing antiviral textiles. The paper furthermore discusses different classes of viruses, how they transmit and replicate, various antiviral agents for textiles and their working mechanism, and the application procedure of various synthesized and bio-based antiviral compounds on textiles.

Viruses and their classification As mentioned earlier, viruses are acellular, considered to be a grey area between the living and the nonliving. Viruses are small protein capsids which store some genetic information. All viruses consist of nucleic acid and a protein coat [21]. The nucleic acid may be either a Deoxyribonucleic Acid (DNA) or a Ribonucleic acid (RNA) but a virus never has both of them. The protein coat encases the nucleic acid while some viruses are also enclosed by a layer of fat and protein molecules called envelopes. The size of the virus varies depending on its structure. In order to reproduce themselves, viruses are dependent on their host cell. Initially, they replicate the genetic information in the cell and produce viral progenies to infect the other cells [22].

Viruses are broadly classified based on their structure, symmetry, chemical composition, structure of genome and on their mode of replication. Based on their genome structure and chemical composition, viruses that infect human beings are divided into twenty-one families [21]. The classification of viruses causing infections in humans is presented in Figure 1.

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divided into twenty-one families [21]. The classification of viruses causing infections in humans is presented in Figure BAR G, 1.

BISWAS D, PATI S, CHAUDHARY K, BAR M. Antiviral Finishing on Textiles … TLR 4 (1) 2021 5-22.

Figure 1. Classification of viruses Figure 1. Classification of viruses

Transmission of viruses A virus can be transmitted in various ways. Virus transmission mainly depends on their ability to overcome a barrier. A virus can transmit from cell to cell, animal to animal, person to person or even from one species to another. It can be transmitted either by a direct contact or by an indirect contact. In the case of a direct contact, the virus is spread from the infected host to an uninfected person by means of a physical touch.

While in the case of an indirect contact, the virus proliferates through different mediums such as textiles, contaminated surfaces etc., sometimes the disease-bearing organisms known as vectors transmit viruses to an uninfected person in the form of blood-sucking insects such as mosquitos [23]. Figure 2 explains the most probable and significant ways in which a virus can infect human beings. Here, infected animals, contaminated areas, and infected persons are considered as major sources of a virus. The droplets released by an infected person or an animal in the form of a cough, sneeze, blood stains etc. make a place or a person contaminated. Droplets having a virus particle of the size less than 1 μm contribute to the spread of airborne diseases [22]. According to Wells [24], the aqueous part of a droplet evaporates quickly in the air and the residue called the droplet nuclei spreads around the corners and ultimately contaminates the place and the people who are sharing the same air supply. Some viruses have large particles, which makes them heavy, and as a result they don’t contribute to the spread of airborne diseases. The transmission of these heavy viruses is greatly influenced by their lifespan outside a host cell. For instance, a SARS-CoV-2 can survive about 24 hours on a cardboard and 3 to 4 days on plastics and stainless steel [25], while an astrovirus, Hepatitis A and Polio virus can survive up to 2 months [26]. The long lifespan outside a host cell makes these viruses deadlier for a human being. However, the researchers have observed that most of the health-related issues in human beings are caused by micro-sized virus particles with the aerodynamic diameter less than 1 μm [22].

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Figure 2. Modes of virus transmission

Replication of viruses

Figure 2. Modes of virus transmission

Replication of viruses Viral replication is a biological process that produces new viruses during the infection of the host cell.

Hence, prior to replicati on, a virus has tothat enter its hostnew cell fiviruses rst. Without host-cell a virus cannot repliViral replication is a biological process produces duringathe infection of the host cell. cate itself as it doesn’t have any organelles such as nuclei, mitochondria, ribosomes and the cytoplasmic Hence, prior to replication, a virus has to enter its host cell first. Without a host-cell a virus cannot components which are necessary for the synthesis of its own structure [23]. During viral replication, initireplicate as or it adoesn’t have anyitself organelles such as nuclei, mitochondria, ally, a virus itself particle virion att aches to the host-cell membrane and injectsribosomes its DNA orand RNAthe into thecytoplasmic host cell tocomponents initiate the infecti general, for a virus a human hoststructure cell through membrane whichon. areInnecessary the enters synthesis of its own [23].the During viral fusion method.initially, Once a avirion its or host cell, the viral genome gets to itsmembrane host cell organelles and replication, virusenters particle a virion attaches itself to theaccess host-cell and injects enzymes. This ultimately initiates the process of the replication of the viral nucleic acid (either DNA or RNA) its DNA or RNA into the host cell to initiate the infection. In general, a virus enters a human host cell and the structural protein with its code. This newly synthesized nucleic acid and the structural proteins are through membrane method.

Once athese virion enters its leave host the cell,host thecell viral genome then joinedthe together as newfusion virus parti cles. Finally, new viruses either by cellgets lysis oraccess by the to budding and become to infect other host initiates cells [27].the process of the replication its hostprocess cell organelles and ready enzymes.

This ultimately of the viral nucleic acid (either DNA or RNA) and the structural protein with its code. This newly

Role of textiles in protection against viruses

synthesized nucleic acid and the structural proteins are then joined together as new virus particles.

As mentioned earlier, viruses are considered to be a grey area between the living and the non-living, and Finally, these new viruses leave the host cell either by cell lysis or by the budding process and they need a host cell to replicate themselves. Thus, a virus will not be able to replicate itself on a textile become ready totexti infect host [27]. surface.

However, lesother can act as cells an acti ve medium for the viral transmission [28,29]. Frequent disinfection or disposal of the contaminated textiles could be an effective way of restricting viral transmission Role oftexti textiles in protection viruses through les [30].

The secondagainst possible way would be to impart antiviral properties to textiles. A normal texti fabric does not have anyare anticonsidered viral properti es but thearea incorporati onthe of living suitable into As le mentioned earlier, viruses to be a grey between andcomponents the non-living, textiles can make them antiviral. The incorporation of an antiviral agent into textiles can be done at diffeand they need a host cell to replicate themselves. Thus, a virus will not be able to replicate itself on a rent stages and in different ways. Various ways of developing antiviral textiles are discussed in the next textile However, can act an active medium forbythe viral transmission 29]. secti on ofsurface. this paper.

Antiviraltextiles agents make theas treated textiles antiviral employing either of the[28, following two mechanisms or by combining the first mechanism, the applied chemicalway makes the surface Frequent disinfection or disposalthem. of theIncontaminated textiles could be an effective of restricting energy of a textile surface relatively low. Doing so will stop the viral transmission via textiles by restricting viruses to the textile surface. This low surface energy of textiles can also destroy the outer lipid barrier of 8 www.textile-leather.com

the viral genome inactive by making it unable to penetrate into a host cell [31]. In the second approach, when a virus comes in contact with a textile surface treated with an antiviral agent, these

BAR G, BISWAS D, PATI S, CHAUDHARY K, BAR M. Antiviral Finishing on Textiles … TLR 4 (1) 2021 5-22.

active agents bind with the outer layer of the virus and inhibit its vital mechanisms. These antiviral

agents oxidize and dissolve the lipid or the glycoprotein layer and enter inside the virus structure. a virus which will make the viral genome inactive by making it unable to penetrate into a host cell [31]. In Finally, these antiviral agents adhere to the genome (i.e. with the virus DNA or RNA) and deactivate the second approach, when a virus comes in contact with a textile surface treated with an antiviral agent, the same breaking intothe fragments.

As of a result of these interactions, the disintegration the these activebyagents binditwith outer layer the virus and inhibit its vital mechanisms.

Theseofanti viral agents oxidize manifesting and dissolveitself the lipid orleakage the glycoprotein layer and enter virus structure. virus ensues, in the of the viral genome and ainside loss ofthe infectivity, leavingFinally, the these antiviral agents adhere to the genome (i.e. with the virus DNA or RNA) and deactivate the same by viral particle inactive on the treated textile surface [7, 32, 33]. A schematic diagram explaining the breaking it into fragments. As a result of these interactions, the disintegration of the virus ensues, manifeantiviral mechanism through virus destruction (i.e. through the second approach) is shown in Figure sting itself in the leakage of the viral genome and a loss of infectivity, leaving the viral particle inactive on 3. treated textile surface [7,32,33]. A schematic diagram explaining the antiviral mechanism through virus the destruction (i.e. through the second approach) is shown in Figure 3.

Figure 3. Antiviral mechanism through virus destruction on textile fabric surface Figure 3. Antiviral mechanism through virus destruction on textile fabric surface

Antiviral treatments for textiles Inherently, textile materials are not antiviral. Textile materials are susceptible to microbial growth due to their high moisture retention and surface area [14]. The addition of suitable antiviral agents onto textiles can make them antiviral. The incorporation of an antiviral agent into the textiles can be done at different stages and in different ways. Antiviral finishing on the textile material can be done onto the textile fibre, yarn, fabric, and final products depending upon the antiviral agents and their application technique. For ease of application and continuous production, antiviral application onto the fabric is preferable. For fabric like cotton, wool, silk, and other manmade fibre, antiviral treatment is done by surface treatments, like the exhaust method, the pad-dry-cure method, microencapsulation, and the coating technique, alone or in combination, depending on the antiviral composition and the fabric quality. Antiviral agents can also be incorporated in manmade fibres by mixing suitable antiviral agents into the polymer matrix before the fibre extrusion [34,35].

The exhaust method is the most common and popular method of dyeing and finishing textile materials. This method is also well suited for the antiviral finishing of natural fibres and polyamide fabrics. The process is very similar to the dipping technique and application is carried out below the boiling temperature. For polyester fabric, the high-temperature exhaust method is preferable. The process is very similar to disperse dyeing and the application is carried out at 120-130 °C. The pad-dry-cure method is another way of applying

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an antiviral composition onto the textile material. The fabric is padded with the antiviral composition in an aqueous medium along with a suitable binder, followed by drying and curing for proper fixation. This method is used alone or in combination with other techniques [36,37,38].

Micro-encapsulation is a process in which an active ingredient as a core substance is generally stored within a polymeric shell. For antiviral finishing on the textile material, a microcapsule solution is prepared by mixing and stirring the antiviral composition and the polymeric coating material in an emulsion reactor at 1000–10000 rotations per minute for 6–48 hours. The size of a microencapsulated shell generally varies within the micrometre and the millimetre range. This antiviral microcapsule solution is applied onto the textile substrate along with other binding compositions in an agitator, followed by drying and curing. This technique is gaining popularity in the area of textile finishing, especially for the fragrance finish, antimicrobial finish etc. for sportswear and medical textiles [39,40,41].

In the coating technique, the covering material is deposited onto the textile substrate to enhance the surface properties. Likewise, in textiles, the fabric can be coated with an anti-pathogenic component along with a suitable binding agent. The preferred coating techniques are reverse roll, rod, spray, and gravure coating techniques. The coating technique requires a substrate with minimum porosity. Most of the non-woven substrates are porous; therefore, alternate versions of the coating technique can be used, such as spray and dip-coating techniques. In certain applications, there might be a need for the controlled release of antiviral agents. In that case, the coating may include microencapsulation. The coating can be of a single layer as well as multi-layered. In multi-layered coating, initially, the substrate is coated with an active ingredient solution by using the spray-coating method and on top of that, the second layer is coated with the binding solution by using the rod-coating method [42].

Triclosan based antiviral finish Triclosan is well known for its antimicrobial activity, especially against bacteria [36, 43]. However, a textile fabric can exhibit an antiviral property when it is treated with triclosan along with sodium pentaborate pentahydrate. The chemical structures of triclosan and sodium pentaborate pentahydrate molecules are shown in Figure 4. Iyigundogdu et al. [36] have prepared a triclosan-based antiviral solution which contains 0.03% triclosan, 3% sodium pentaborate pentahydrate and 7% glucapon 215 CS UP. A cotton fabric, treated with the abovementioned antiviral solution for 30 minutes by the exhaustion method at pH 5 exhibits promising results against the adenovirus and poliovirus. Glucapon 215 CS UP acts as an emulsifying agent and the triclosan inhibits the growth of viruses by restricting lipid biosynthesis. The function of sodium pentaborate pentahydrate in the above composition is not well understood but its presence enhances the antiviral activity of the triclosan. According to the Spearman–Karber test method, a cotton fabric treated with the abovementioned solution can reduce the viral titre by 60%. Iyigundogdu et al. [36] have predicted that the textiles treated with the combination of triclosan and sodium pentaborate pentahydrate can be effective against the enveloped and non-enveloped DNA and non-enveloped RNA viruses, such as hepatitis B, HIV, HCV, Ebola, MERS and SARS.

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be effective against the enveloped and non-enveloped DNA and non-enveloped RNA viruses, such as hepatitis B, HIV, Ebola,D,MERS and SARS. K, BAR M. Antiviral Finishing on Textiles … TLR 4 (1) 2021 5-22.

BARHCV, G, BISWAS PATI S, CHAUDHARY BAR G, BISWAS D, PATI S, CHAUDHARY K, BAR M. Antiviral Finishing on Textiles … TLR 0 (0) 2020 00-00.

Treatment with honeysuckle extract Since ancient times, honeysuckle has been used as a traditional Chinese medicine for the treatments of wind-heat, respiratory tract infection, fever and inflammatory conditions [46]. The honeysuckle extract is rich in chlorogenic acid, which acts as an antiviral agent. Chlorogenic acid suppresses the viral mRNA Figure transcription and the (a) subsequent translation.

The chemical 4. Chemical structure Triclosan (b) protein Sodium pentaborate pentahydrate [44, 45] structure of Figure 4. Chemical (b) Sodium pentahydrate chlorogenic acid is shown in structure Figure 5.(a)ItTriclosan is reported thatpentaborate chlorogenic acid can[44, be45] effective against

Treatment with honeysuckle extract

several viruses, including HIV, adenovirus, hepatitis B and HSVs. [2, 47]. Textile material can be Since ancient times, honeysuckle has beenby used a traditional Chinesetechnique. medicine for treatments of windtreated with the honeysuckle extract theasmicroencapsulation In the microencapsulation, heat, respiratory tract infection, fever and inflammatory conditions [46]. The honeysuckle extract is rich in an active chemical agent is generally stored within a polymeric shell. The size of a microencapsulated chlorogenic acid, which acts as an antiviral agent. Chlorogenic acid suppresses the viral mRNA transcription shell varies within the micrometre and the millimetre range [40,acid 41].isJinmei and thegenerally subsequent protein translati on. The chemical structure of chlorogenic shown(Patent in FigureNo. 5. It is CN101324026B, reported that chlorogenic can be that effecti ve against severalfabric viruses, including HIV, adenovirus, hepa2011) hasacid observed treating a cotton with a drug-component solution titicontaining s B and HSVs. [2,47]. Texti le material be Glycyehizae treated with(20% the honeysuckle by forsythia the microencaphoneysuckle (30% to 60%),can Radix to 50%) andextract Weeping (20% sulation technique. In microencapsulation, an active chemical agent is generally stored within a polymeric to 50%) extracts by using the microencapsulation technique imparted antiviral properties to the shell. The size of a microencapsulated shell generally varies within the micrometre and the millimetre range fabric Jinmei surface.(Patent The microcapsules were prepared using the above withwith polylactic [40,41].

No. CN101324026B, 2011) has observed that drug treatisolution ng a cottalong on fabric a drugcomponent containing honeysuckle (30% to 60%), Glycyehizae (20% 50%) and applied Weeping acid (masssoluti ratioon 1:2) in an emulsion reactor.

Further, theRadix microcapsules (30% to to 60%) were forsythia (20% tofabric 50%)along extracts using zinc the microencapsulati ontotechnique antipolyurethane viral properties onto a cotton withby a nano oxide solution (5% 20%), andimparted an aqueous to the fabric surface. The microcapsules were prepared using the above drug solution along with polylactic solution (10% to 15%), followed by curing at 150 °C [41]. The preparation of microcapsules and their acid (mass ratio 1:2) in an emulsion reactor. Further, the microcapsules (30% to 60%) were applied onto a application onto with the acotton fabric is soluti illustrated 6. an The nano polyurethane zinc oxide has excellent cott on fabric along nano zinc oxide on (5%intoFigure 20%), and aqueous soluti on (10% topathogen 15%), followed curing at 150 °C [41].the Theaqueous preparati on of microcapsules andmicrocapsules their applicatiand on onto the killingby properties, whereas polyurethane binds the nano cotton fabric is illustrated in Figure 6. The nano zinc oxide has excellent pathogen killing properties, whereas zinc oxide to the cotton fabric. The finished fabric is friendly to the skin and it shows an antiviral the aqueous polyurethane binds the microcapsules and nano zinc oxide to the cotton fabric. The finished activity even after 20 washes with a virus inhibitory rate of more than 80% against the influenza and fabric is friendly to the skin and it shows an antiviral activity even after 20 washes with a virus inhibitory herpes simplex rate of more thanvirus 80% [41]. against the influenza and herpes simplex virus [41].

Figure 5. Chemical structure of chlorogenic acid [48] Figure 5. Chemical structure of chlorogenic acid [48]

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Figure andtheir theirapplication applicationonto ontocotton cotton fabric using honeysuckle extract Figure6.6.Preparation Preparationof ofantiviral antiviral microcapsules microcapsules and fabric byby using honeysuckle extract

Povidone coatedtextiles textiles Povidone iodine-based iodine-based coated Ripa et al. [43] have reported that iodophors i.e. povidone iodine and tinctures of iodine have excellent Ripa et al. [43] have reported that iodophors i.e. povidone iodine and tinctures of iodine have antimicrobial effectiveness against a broad spectrum of viruses. Almost all microorganisms causing human excellent antimicrobial effectiveness against a broad spectrum of viruses. Almost all microorganisms disease are susceptible to free iodine released by the povidone iodine complex. Povidone iodine can be causingonto human disease are susceptible free released byngthe povidone iodine applied the texti le materials to make ittoanti viraliodine by using the coati technique.

Coati ng is complex. a technique through which functi onal are layered onto materials a substratetotomake enhance the surface properti Uniform Povidone iodine can bematerials applied onto the textile it antiviral by using thees. coating coating over a textile surface can be applied by using reverse roll, rod and gravure coating techniques. technique. Coating is a technique through which functional materials are layered onto a substrate to Coating can be of a single layer as well as multi-layered. The multi-layer coated fabric shows better antiviral enhance surface properties.

Uniform coating over a textile surface canwhich be applied byan using properti es.the Snyder (Patent No.US5968538A, 1999) prepared a coating solution contains active reverse roll, rod and techniques.

Coating be of acomprised single layer wellofas multiingredient (71.5%) and gravure a premixcoating solution (28.5%). The activecan ingredient ofas 6.7% Nonoxynol 9layered.

(N9) and The 93.3%multi-layer of polyvinyl-pyrrolidone-iodine complex (PVP-I).

The premix solution which acted as a coated fabric shows better antiviral properties.

Snyder (Patent binder was comprised of 54.6% of polyethylene glycol, 5.4% of hydroxypropyl methylcellulose, 7.2% of No.US5968538A, 1999) prepared a coating solution which contains an active ingredient (71.5%) and polyoxyethylene sorbitan, 11.5% of hydrous magnesium silicate and 21.3% of ethanol. The combination of a premix (28.5%).

The active ingredientproperti comprised ofthe 6.7% of Nonoxynol 9 (N9) and 93.3% on of of PVP-I and solution N9 imparted antiviral and hydrophilic es to coated substrates.

Upon absorpti polyvinyl-pyrrolidone-iodine complex (PVP-I). free The iodine premixwhich solution which acted as a [42]. binder was moisture by the coating material, PVP-I releases acts against the viruses According tocomprised Bigliardi etof al. 54.6% [32] freeofiodine has excellent penetrati against biofi lms, which accelerates polyethylene glycol, 5.4%onofcapacity hydroxypropyl methylcellulose, 7.2% ofthe 12 www.textile-leather.com

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penetration of iodine through the virus cell wall. The virucidal activity of iodine involves the inhibition of vital mechanisms by oxidizing the fatty/amino acid and deactivating the proteins as well as DNA or RNA [49]. It is observed that antiviral effectiveness of the 10%-povidone-iodine exhibits promising results against certain viruses as compared to polyhexanide, chlorhexidine and the 70%-ethanol [42].

Antiviral textiles treated with copper compound Textile materials treated with copper-based compounds show excellent antibacterial properties which inspire the researchers to study its influence against the viruses. Organic and inorganic colloidal, nanosized copper-compound particles can be applied onto textile substrates in various ways, such as the hightemperature exhaust process, sol-gel process, foulard, and spray method [37]. According to Borneman [37], a polyester fabric was treated with copper pigments in mild acidic condition by using the high-temperature exhaust process. Further, the treated fabric was padded with a polymer binder and was cured subsequently to fix the copper pigment over the fabric surface. The antiviral test result indicated that the finished fabric was efficiently hygienic when tested against the bacteriophage MS2. It absorbed 91% of the virus from the affected source and at the same time 90% of the virus concentration was reduced in the cloth [37]. The copper released electrically positive charged particles which broke the outer membrane of the virus. They also destroyed the genetic compound, thereby making it impossible for the virus to replicate [50,51]. According to current research, copper particles interact with the oxygen molecule to form a reactive oxygen species (ROS). The ROS reacts to inactivate the virus, it results in fragmentation of the genome of the virus on the copper surface, ensuring that the inactivation is irreversible [52].

Fujimori et al. (Patent No. EP2786760A1, 2014) have observed that when a fibre having a carboxyl functionalgroup is impregnated in the dispersed divalent copper compound solution, a salt-stabilizer is required to control the uniform attachment of the divalent copper ion onto the fibre surface. This restricts the amount of the copper compound that can be attached to the fibre, thus leading to insufficient antiviral performance. Antiviral activity of these fibres can be improved further by using a monovalent copper compound like CuCl, CUI, CuBr etc. or an iodide compound of Cu, Ag, Sb, Ir, Ge, Sn, Tl, Pt, Pd, Bi, Au, Fe, Co, Ni, Zn, In or Hg, instead of a divalent copper compound. Test result indicates that copper (I) chloride (CuCl) gives best antiviral effectiveness compared to the other compounds mentioned above. The dispersed CuCl solution can be applied over all kinds of textile surfaces with the help of a binder, which immobilizes the CuCl on the fabric surface. Antiviral synthetic fibre can be produced by adding CuCl to the molten polymer before the extrusion of fibre [53]. According to Gabbay (Patent No. US7169402B2, 2007), an antiviral synthetic fibre can be produced by adding ionic copper powder having particle size below 10 microns to the polymer slurry before the extrusion with a solid content range from 0.25% to 10%. It was observed that the active copper particles encapsulated in the fibre with certain portions protrude and expose from the surface of the polymeric fibre and make the fibre antiviral. Test result proclaims that viral inactivation rate of 0.25% of CuCl is 99.9999% against influenza and Feline Calicivirus with the exposure time of only 1 minute [54].

Diaz (Patent No. WO2015035529A2, 2015) has claimed that an antiviral fabric can be produced by using copper filaments. A plied yarn was produced by using copper filament along with a textile yarn, as shown in Figure 7. Further, this yarn was converted to a textile fabric. In contact with the atmospheric oxygen, the copper filament oxidizes into cuprous oxide and cupric oxide. These copper oxides form a layer on the copper surface and release positively charged copper ions which further inactivate the virus [55].

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textile fabric. In contact with the atmospheric oxygen, the copper filament oxidizes into cuprous oxide and cupric oxide. These copper oxides form a layer on the copper surface and release positively BAR G, BISWAS D, PATI CHAUDHARY BAR M. Antiviral Finishing charged copper ionsS,which furtherK,inactivate the virus [55].on Textiles … TLR 4 (1) 2021 5-22.

Figure 7.

7. Plied Pliedyarn yarnwith withcopper copperasasa acomponent component Figure

Metal basedantiviral antiviral textiles Metal phthalocyanine phthalocyanine based textiles Phthalocyanines been used for photodynamic therapy in medical science science since long ago.long PhthalocyaPhthalocyanineshave have been used for photodynamic therapy in medical since ago. nines can photosensitize by absorbing light in the presence of oxygen leading to the generation of an excited Phthalocyanines can photosensitize by absorbing light in the presence of oxygen leading to the sensitizer. The excited sensitizer modifies the biomolecules, such as amino acids, protein, lipid and nucleic BAR D, sensitizer.

PATI S, leads CHAUDHARY BAR M. on Antiviral Textiles TLR 0such (0) 2020 00-00. generation ofG, anBISWAS excited The sensitizer theonbiomolecules, as amino acid by oxidati on reacti on which to excited the K, inacti vati ofmodifies theFinishing microbes [56,57].…Metal phthalocyanine compounds can be applied onto theacid textiby lesoxidation by using the ionic dyeing et al. (Patent acids, protein, lipid and nucleic reaction whichmethod. leads toMatsushita the inactivation of theNo. EP2243485A1, 2010), cationized a rayon fabric by dipping it into a solution containing 50g/L of cation UK, microbes [56, 57].

Metal phthalocyanine be of applied ontophthalocyanine. the textiles by using phthalocyanine derivative and enhances compounds the antiviral can effect the metal Cobaltthe (II) a cationic agent and 15g/L of sodium hydroxide for 45 min, at 85 °C having material to liquor ratio of 1:10. ionic dyeing method.

Matsushita et cobalt al. (Patent No. EP2243485A1, 2010), acid cationized rayon fabric by phthalocyanine monosulfonic (II)1% phthalocyanine disulfonic can beareplaced by cobalt iron Further, the cationized fabric wasand treated with cobalt (II) phthalocyanine monosulfonic acid and dipping it into a disulfonic solution containing 50g/L of cation UK,adjusted a cationic agent hydroxide andFigure 15g/Lsoluti sodium (II) phthalocyanine acid in a strong alkaline medium byproperties. sodium on (pH 12) (III) phthalocyanine tetracarboxylic acid to obtain similar antiviral 8 ofshows the athydroxide 80 °C by using exhaust cationizati onmonosulfonic treatment the carrier eff ect of the metal for 45the min, 85method. ℃ having material to liquor ratio ofimproves 1:10.

Further, the fabric chemical structure ofat cobalt (II) The phthalocyanine acid, cobalt (II)cationized phthalocyanine phthalocyanine derivative and enhances the antiviral effect of the metal phthalocyanine. Cobalt (II) phthawas treatedacid withand 1% iron cobalt(III) (II) phthalocyanine phthalocyanine tetracarboxylic monosulfonic acid cobalt (II) phthalocyanine disulfonic acid.and Metal phthalocyanines have locyanine monosulfonic and cobalt (II) phthalocyanine disulfonic acid can be replaced by iron (III) phthadisulfonic acidcatalytic in a strong alkaline medium adjusted byproperti sodium hydroxide (pH 12) at 80structure °C the by enzyme-like activity it has been that protein denaturation ischemical induced by locyanine tetracarboxylic acid to and obtain similar antifound viral es.

Figure 8solution shows the the method.

The cationization treatment improves the carrier acid effect ofiron the metal ofusing cobalt (II) exhaust phthalocyanine acid,functions cobalt (II) of phthalocyanine disulfonic and (III) phthaadsorptive properties andmonosulfonic redox catalytic the metal phthalocyanines.

Virus titre test locyanine acid.

Metalby phthalocyanines have enzyme-like catalyti c activityrate andof it has result oftetracarboxylic the rayon fabric treated metal phthalocyanine indicates virus reduction 99%been or found that protein denaturation is induced by the adsorptive properties and redox catalytic functions of the above when tested against the avian influenza virus. However, only cationized rayon fabric shows a metal phthalocyanines. Virus titre test result of the rayon fabric treated by metal phthalocyanine indicates virus reduction rateofof99% 96.83% whichwhen explains theagainst impact the of cationization [38]. virus reducti on rate or above tested avian influenza virus. However, only cationized rayon fabric shows a virus reduction rate of 96.83% which explains the impact of cationization [38].

Figure 8. Chemical structure of (a) cobalt (II) phthalocyanine monosulfonic acid (b) cobalt (II) phthalocyanine disulfonic acid (c) iron (III) phthalocyanine tetracarboxylic [38] Figure 8. Chemical structure of (a) cobalt (II) phthalocyanine monosulfonic acid (b)acid cobalt (II) phthalocyanine disulfonic acid (c) iron (III) phthalocyanine tetracarboxylic acid [38]

Cationic surfactant-based treatment 14 www.textile-leather.com Cationic surfactants synthesized from the condensation of esterified dibasic amino acids and fatty acids are widely used as finishing agents for textiles and as disinfectants in detergents [58]. However,

BAR G, BISWAS D, PATI S, CHAUDHARY K, BAR M. Antiviral Finishing on Textiles … TLR 4 (1) 2021 5-22.

Cationic surfactant-based treatment Cationic surfactants synthesized from the condensation of esterified dibasic amino acids and fatty acids G,as BISWAS D, PATI S, CHAUDHARY BARas M.disinfectants Antiviral Finishing on Textiles[58]. … TLRHowever, 0 (0) 2020they 00-00. are widelyBAR used finishing agents for textilesK,and in detergents can also be used as an effective antimicrobial agent because of their biocidal properties. Quaternary ammonium compounds, a type of a cationic surfactant, are effective against many bacteria as well as enveloped Ethanol improves the permeability of the cationic surfactant into the fibre and helps enhance the viruses, whereas non-enveloped viruses are highly resistant against it [59]. Cationic surfactant having a antiviral effect.group A 99.9% drop inonvirus onsolvent the surface the textile material polyoxyalkylene in combinati with concentration a water miscible exhibitsofanti viral activity againstwas both enveloped non-enveloped viruses ontreated textile materials Tobe et al. (Patent No. JP6519080B2, 2019) observedand when the textile material with the [60]. abovementioned antiviral composition was prepared an antiviral composition containing 0.2% of didecyl methyl poly (oxyethyl) ammonium propionate, tested against Feline calicivirus after leaving it for 1 hour [60]. a cationic surfactant, 10% of ethanol and a water miscible solvent and have treated a textile fabric by using the aerosol spray method, followed by air-drying. The weight pick-up of the textile fabric was restricted to Chitosan based antiviral treatment 50%. Ethanol improves the permeability of the cationic surfactant into the fibre and helps enhance the antiviral ect.of A 99.9% drop in in virus concentrati on on thetextiles surfacehas of the textile material was observed when Theeffuse biomaterials developing protective increased rapidly due to their ecothe textile material treatedand with the abovementi onedAmong antiviral compositionchitosan was tested against Felinefor califriendly, biodegradable non-toxic properties. biomaterials, is widely utilized civirus after leaving it for 1 hour [60]. multi-functional finishes on textile materials such as the antimicrobial finish, mosquito repellent

finish, crease etc. [61, 62]. Chemical structure of chitosan is shown in Figure 9.

Chitosan basedresistant antiviralfinish treatment Chitosan is generally obtained from crab shells, shrimp shells, lobsters as well as the exoskeleton of The use of biomaterials in developing protective textiles has increased rapidly due to their eco-friendly, the zooplankton corals,properti jellyfishes. etc.Among [63, 64, 65]. It contains a large amountuti oflized positively charged biodegradable and like non-toxic biomaterials, chitosan is widely for multi -functional finishes onamino textilegroups materials suchdamage as the anti finish, mosquitoThe repellent finish, crease resistant nucleophilic which themicrobial virus’ cell membrane. effectiveness of chitosan’s finish etc. [61,62]. Chemical structure of chitosan is shown in Figure 9. Chitosan is generally obtained from antiviral activity is enhanced when a textile material is treated with chitosan along with organic acid crab shells, shrimp shells, lobsters as well as the exoskeleton of the zooplankton like corals, jellyfish etc. crosslinking agent, plant extract andofsodium phosphate.

Xinming (Patent Nogroups CN105506984A, 2016) [63,64,65].

It contains a large amount positively charged nucleophilic amino which damage the prepared an antiviralThe solution 0.5% of hydroxypropyl chitosan, 0.6% when of O-carboxymethylvirus’ cell membrane. effecticontaining veness of chitosan’s antiviral activity is enhanced a textile material is N, treated with chitosan along with organic acid crosslinking agent, plant extract acid, and sodium phosphate.

N, N-trimethyl ammonium chloride chitosan, 1% of butane tetracarboxylic 1% of citric acid, Xinming (Patent No CN105506984A, 2016) prepared an antiviral solution containing 0.5% of hydroxypropyl 2% of sodium phosphate, 0.6% of folium artemisiae argyi extract, 0.4% of dandelion extract, 0.6% of chitosan, 0.6% of O-carboxymethyl-N, N, N-trimethyl ammonium chloride chitosan, 1% of butane tetratea extract and of aloe andphosphate, has applied0.6% the of same overartemisiae a textile surface through theof carboxylic acid, 1%0.8% of citric acid,vera 2% extract of sodium folium argyi extract, 0.4% pressure-rolling having the and weight pick-up After that, fabricthe was dried at aabout dandelion extract, process 0.6% of tea extract 0.8% of aloe70-100%. vera extract and hasthe applied same over textile surface through thebaked pressure-rolling process the weight 70-100%.

Afterobserved that, the that fabricthe was 100-120 °C and at 150-190°C for having 2.5-5 minutes.

Onpick-up evaluation, it was dried at about 100-120 °C and baked at 150-190°C for 2.5-5 minutes. On evaluation, it was observed that treated fabric had high efficacy (more than 99.9%) against a broad spectrum of viruses [66]. the treated fabric had high efficacy (more than 99.9%) against a broad spectrum of viruses [66].

Figure 9. Chemical structure of chitosan [67] Figure 9. Chemical structure of chitosan [67]

Antiviral treatment for nonwoven textiles Nonwoven fabrics are a wide range of fibrous materials, which are formed through direct fibre web le-leather.com formation. They are widely used for filtration purposes for their highwww.texti air permeability, abrasion15

resistance, uniform structure, etc. [68]. A nonwoven fabric can also be used for inhibiting the growth

BAR G, BISWAS D, PATI S, CHAUDHARY K, BAR M. Antiviral Finishing on Textiles … TLR 4 (1) 2021 5-22.

Antiviral treatment for nonwoven textiles Nonwoven fabrics are a wide range of fibrous materials, which are formed through direct fibre web formation. They are widely used for filtration purposes for their high air permeability, abrasion resistance, uniform structure, etc. [68]. A nonwoven fabric can also be used for inhibiting the growth of microbes, especially viruses, when treated with acidic polymers. Poly carboxylic acid polymer is preferable as an acidic polymer to treat nonwoven fabric. The acidic polymer can be applied on nonwoven fabric in combination with organic acid, plasticizers or surfactants in different ratios in order to enhance the antiviral performance of the treated fabric. Biedermann et al. (Patent No. WO2008009651A1, 2008) prepared a loading solution containing 2% (w/w) of carbopol ETD 2020, a poly carboxylic acid polymer and 1% (w/w) of citric acid and have coated a polypropylene nonwoven fabric with the abovementioned loading solution. When a virus came into contact with the coated nonwoven surface, it interacted with the acidic polymer and was subsequently entrapped.

The acidic environment (pH 2 to 2.5) of the acidic polymer inactivated and neutralized the virus. A reduction in viral titre around 99.97% was observed when nonwoven fabric coated with the acidic polymer was tested against the avian influenza A NIBRG-14 H5N1 virus with an hour of contact time [69].

Kim (Patent No. KR101317166B1, 2013) treated a nonwoven fabric using the kimchi enzyme to make it antiviral. Kimchi is a type of fermented Korean food. Kimchi enzyme is obtained by culturing the lactic acid bacteria after aging kimchi. An aqueous antiviral solution comprised of kimchi enzyme (10%) and polyvinyl alcohol resin (25%) was prepared and sprayed onto the nonwoven polyester fabric by using the electrospinning method, followed by drying at 100 °C. The finished fabric contained 3% w/w of kimchi enzyme and 7% w/w of polyvinyl alcohol resin. It was observed that the virus log reduction value of the nonwoven fabric treated with kimchi enzyme is more than 4.9 (>99.87%) when tested against the influenza A virus after being incubated for an hour. The ingredients of kimchi, such as green onion and ginger, hinder the virus growth further [70].

Antiviral treatment for nonwoven textiles The idea of developing antiviral textiles is a novel one. Only a few studies on developing antiviral textiles have been carried out and most of these studies have been patented. The viruses for antiviral testing, test conditions etc. are different from one study to another. Hence, very limited information is available for the comparison of existing antiviral textiles. Here, the effectiveness of antiviral finish and its durability are considered for the comparison of various antiviral finished textile materials. The effectiveness of an antiviral textile material depends on the antiviral compounds used and the virus against which the material is being tested. It is observed that textile materials treated with monovalent copper compound, metal phthalocyanine, acidic polymer and kimchi enzyme showed a virus reduction rate of more than 99% when tested against the influenza virus [38,53,54,69,70]. Textiles treated with a cationic surfactant and textiles treated with chitosan show a similar result when tested against the feline calicivirus [60,66].

Durability of the antiviral finish on the textile material depends on how frequently the product is washed.

In the case of single-use health care and hygiene products, durability is least important while in the case of daily used apparel and home textile products, durability influences its effectiveness. It is observed that fabrics treated with the honeysuckle extract, chitosan, kimchi enzyme and metal phthalocyanine are durable for several washes [38,41,66,70]. The premix binder solution makes textile material coated with povidone iodine durable and imparts sanitizing activity to the finished product [42], whereas textile materials treated with a cationic surfactant are semi-durable. Along with effectiveness and durability, skin-friendliness is another important parameter which determines whether the finished textile is suitable for garment manu16 www.textile-leather.com

BAR G, BISWAS D, PATI S, CHAUDHARY K, BAR M. Antiviral Finishing on Textiles … TLR 4 (1) 2021 5-22.

facturing or not. Kimchi enzyme, chitosan and honeysuckle are extracted from bio-sources. The treated textile materials are safe for the skin when these bio-extracts are applied onto the textile fabric within the permissible limit [41,66,70]. Textile materials treated with acidic polymer and a cationic surfactant are also skin-friendly as the abovementioned chemicals exhibit excellent antiviral property at a very low add-on level. Polyester fabric treated with the copper pigment and CuCl gives excellent antiviral activity but these are not recommended for apparel as they induce skin irritation in case of direct and prolonged contact with the skin [53,54,71].

Possible areas of application of antiviral textiles Looking at the outbreak of deadly viruses in the past and considering the ongoing pandemic scenario, the antiviral property should be one of the most desirable requirements for any textile product. However, textile materials are not inherently antiviral, they need to be treated with some suitable chemical agents to impart the antiviral property. This treatment raises the cost of the finished product and, moreover, not all antiviral agents are environment friendly. Thus, one should use antiviral textiles where it is necessary.

The healthcare sector should be the prime consumer of antiviral textiles, as the personnel connected to this sector deals with the virus-affected patients directly. Depending upon the number of uses, the textile for healthcare sector are of two types, namely single-use products and multiple-use products. Surgical gowns, surgical caps, facemasks etc. are the example of some single-use textile products while the patients’ bed covers, pillow covers, window curtains etc. are the example of multiple-use products. The singleuse textiles can be treated with non-durable antiviral agents while the durability of the antiviral finishing is one of the major requirements for the multiple-use products. After healthcare, the public transport sector should be the next major consumer of antiviral textiles. Majority of the world’s population depends on public transport on a daily basis which increases the probability of virus transmission followed by surface contamination. Therefore, there is a great scope of use for the antiviral polyester fabric treated with CuCl or polyester fibres embedded with ionic copper powder by dope finishing for seat covers and curtains in buses and trains because of their high antiviral efficacy and excellent dirt-cleaning efficiency. Furthermore, train and bus seat covers can also be coated with povidone iodine and nonoxynol 9 coating solution for their self-sanitizing activity. Like healthcare and public transport sectors, textile materials used in hospitality sectors should have antiviral properties. In hotels, bed linens, table linen and bath linen are frequently used by different customers. To prevent the possibility of any viral transmission the above textile products should be treated with some suitable antiviral agents. During the pandemic situation, antiviral properties are preferable for the garments also. Fabrics treated with the honeysuckle extract, chitosan and kimchi enzyme are durable for up to several washes. The abovementioned antiviral agents are bio-based and do not have any adverse effect on human skin. The fabrics treated with the abovementioned antiviral compounds can be used for outerwear garments, like shirts, T-shirts, trousers, tops, skirts and bottoms. These fabrics can also be used for sportswear and military wear. For instant antiviral effect, any type of textile products can be treated with a cationic surfactant-based antiviral composition by using the dipping or spraying method, followed by air drying.

CONCLUSION Looking at the current scenario, the need for antiviral textiles is becoming essential. Researches are being carried out to keep up the pace with the market demand and safety of the people. Textile materials are treated with various synthesized chemicals such as triclosan, copper compound, acidic polymer, povi-

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BAR G, BISWAS D, PATI S, CHAUDHARY K, BAR M. Antiviral Finishing on Textiles … TLR 4 (1) 2021 5-22.

done iodine, cationic surfactant, and metal phthalocyanine as well as with some natural extracts such as honeysuckle extract, chitosan and kimchi enzyme, in order to impart antiviral property to them. Most of these textiles treated with chemicals and bio-extracts show excellent antiviral property against a wide spectrum of viruses. Keeping the disastrous viral diseases and pandemics in mind, the above antiviral agents can be applied onto various textile products to fight against the SARS-CoV-2 virus, thereby providing a meaningful solution for saving the mankind. Antiviral textiles continue to be one of the most dynamic fields of research and one that needs to be on the lookout for novel technologies.

Declaration of conflicting interests The authors declare no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding The author(s) received no financial support for the research, authorship, and/or publication of this article.

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[47] Zhou Y, Tang RC. Facile and eco-friendly fabrication of AgNPs coated silk for antibacterial and antioxidant textiles using honeysuckle extract. Journal of Photochemistry and photobiology B: Biology. 2018;178:463471.

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2014;2014:1–10. https://doi.org/10.1155/2014/726585 [49] Bigliardi P, Langer S, Cruz JJ, Kim SW, Nair H, Srisawasdi G. An Asian Perspective on Povidone Iodine in Wound Healing. Dermatology. 2017;233(2–3):223–233. https://doi.org/10.1159/000479150 [50] Borkow G. Using Copper to Fight Microorganisms. Current Chemical Biology. 2012;6(2):93–103. https:// doi.org/10.2174/187231312801254723 [51] Borkow G, Gabbay J. Putting copper into action: copper‐impregnated products with potent biocidal activities. The FASEB Journal. 2004;18(14):1728–1730. https://doi.org/10.1096/fj.04-2029fje [52] Warnes SL, Little ZR, Keevil CW. Human Coronavirus 229E Remains Infectious on Common Touch Surface Materials. mBio. 2015;6(6):1-10. https://doi.org/10.1128/mbio.01697-15 [53] Fujimori Y, Nakayama T, Sato T. Antiviral agent. European Patent No. EP2786760A1, 2014.

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[66] Xinming X. Method for performing antibacterial and antivirus treatment on textiles by utilizing natural biomaterials, China Patent No CN105506984A, 2016.

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MAHMUD Y, et al. Assessment of the Carbon Footprint and VOCs Emissions … TLR 4 (1) 2021 23-29.

Assessment of the Carbon Footprint and VOCs Emissions Caused by the Manufacturing Process of the Footwear Industry in Bangladesh Yead MAHMUD, Md. RASHED-UL-ISLAM*, Md. Obaidul ISLAM, Tanvir Siddike MOIN, Khandaker Tanzim RAHMAN Institute of Leather Engineering and Technology, University of Dhaka, Dhaka-1209, Bangladesh *rashed.ilet@du.ac.bd Article UDC 685.34:614.71 DOI: 10.31881/TLR.2020.19 Received 20 September 2020; Accepted 22 October 2020; Published Online 5 November 2020; Published 2 March 2021

ABSTRACT Every industry has an impact on the environment, either good or bad, and leather and footwear industries are no exception. For the footwear industry, the main environmental impacts are the releasing of volatile organic compounds (VOCs) and solid wastes. The pressure of reducing harm to the environment is coming from both the consumers and the legislation. CO2 and VOCs are hazardous to human health and also trigger serious environment problems, such as ozone layer depletion, offensive odour, photochemical smog, acid rain and many others. Adhesives, finishing products and cleaners contribute to VOCs emissions in the footwear manufacturing industry. VOCs emission may also arise from primers, separating agents, printing inks or finishing pastes.

Some most commonly produced VOCs in the footwear manufacturing industry are benzene, toluene, styrene, ethylene, xylene, acetaldehyde, formaldehyde, methyl ethyl ketone, chlorobenzene, phenol etc. All of these cause severe health problems in humans and have an adverse effect on the environment. An increasing number of footwear factories adversely affects the environment and human health. One of the largest environmental impacts of shoe industry comes from the manufacturing stages of the shoe’s life cycle. This study was carried out to measure the carbon footprint and VOCs emissions among ten selected footwear factories. The results revealed that the total energy footprint for one pair of shoes is 18.004826 MJ, the water footprint is 8.37167 litres and the carbon footprint is 9.174979 kg CO2 eq. The highest impact in terms of the carbon footprint lies in the shoe manufacturing process with a 5.85109 eq. CO2 (kg). The total VOCs consumption for a fashion shoe is around 36.5 g/pair on average. There should be an initiative taken with the aim of adjusting the choice of methods, materials, machines and the monitoring systems as well as the safety policy for the workers and the environment.

KEYWORDS Carbon footprint, VOCs, Footwear, Pollution

INTRODUCTION The footwear industry is not considered particularly harmful for the environment. However, producing and using shoes on a grand scale has the potential for generating significant harmful environmental impacts.

According to the ‘World Footwear Yearbook’ the worldwide production of footwear reached 23.0 billion pairs. Bangladesh has been ranked eighth in terms of footwear production in the world in 2016, producing www.textile-leather.com 23

MAHMUD Y, et al. Assessment of the Carbon Footprint and VOCs Emissions … TLR 4 (1) 2021 23-29.

370 million pairs of shoes or 1.6 percent of the total output. A Study shows that a typical pair of running shoes made of synthetic materials is 14 ± 2.7 kg of CO2 eq. during its life cycle. A single shoe can contain 65 discrete parts that require 360 processing steps for the assembly [1]. These processes involved in footwear manufacturing, like pattern making, cutting, sewing, lasting and finishing, are all associated with different types of health hazards. But most insidious of all are the toxic organic solvents which are particularly present in the adhesives and also in the hardeners, cleaning solutions and degreasers used in the shoemaking process [2].

The footwear sector of Bangladesh is now at a stage where it can have a larger role in country’s export fortunes in the next decade. According to the Leather Goods and Footwear Manufacturers and Exporters Association of Bangladesh (LGFMEAB), more than 51 of the foreign companies have expressed their interest to establish joint-venture footwear units in Bangladesh [3]. Bangladesh has become an attractive destination for investors from different countries due to some influencing factors like low labour cost, availability of raw materials, good quality product, exchange rate advantage etc. [4]. The increasing number of footwear factories negatively affects the environment and human health. One of the largest environmental impacts of shoes comes from the manufacturing stage of shoe’s life cycle; and surprisingly, the majority of the people who have participated in a survey on this subject believes that shoes only have an environmental impact after they have been thrown out. In the stage of manufacturing, vast amounts of machines and chemicals are required to produce shoes. To power these machines, a great amount of fossil fuels is needed and these fossil fuels produce greenhouse gases when burned. Coal is one of the sources of energy that is very often used to power these factories as it is quite cheap compared to oil or other sources of energy. Burning coal produces carbon dioxide, which eventually ends up in our atmosphere, contributing to the greenhouse effect [5].

The footwear manufacturing process includes exposing a number of harmful compounds, such as volatile organic compounds, toxic organic solvents, hydrocarbons, adhesives, shoe polishes etc. [6]. VOCs are injurious to human health and also trigger serious environmental problems, such as ozone layer depletion, offensive odour, photochemical smog and acid rain. Adhesives, finishing products and cleaners contribute to VOCs emissions in the footwear manufacturing industry. VOCs emissions may also arise from primers, separating agents, printing inks or finishing pastes. Some of the most commonly produced volatile organic compounds in the footwear manufacturing industry are benzene, toluene, styrene, ethylene, xylene, acetaldehyde, formaldehyde, methyl ethyl ketone, chlorobenzene, phenol etc. All of these cause severe health problems in humans and have a negative effect on the environment as well. Therefore, up-to-date information is essential for the industry owners to take proper action in preventing and minimizing the load of pollution caused by the carbon footprint and VOCs emissions. The aim of this paper was to measure the amount of the carbon footprint and VOCs emissions caused by the footwear industry and assess its current state.

EXPERIMENT Materials and Methods For this research 10 factories for the carbon footprint and VOCs emissions analysis were selected. The study was carried out from October 2018 to April 2019. The geographical locations of the factories are from Dhaka to Gazipur.

The LCA measuring SimaPro software version 8 was chosen for measuring the carbon footprint and the VOC Environmental Meter (PCE-VOC) {measuring range 0.00 … 9.99 ppm or mg/m3, resolution 0.01 ppm or mg/m3, accuracy ± 5% of measured value} was used to measure the amount of volatile organic compounds emissions from the selected footwear factories.

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MAHMUD Y, et al. Assessment of the Carbon Footprint and VOCs Emissions … TLR 4 (1) 2021 23-29.

Measurement of Carbon Footprint The carbon footprint was measured by breaking down the materials needed for producing one pair of shoes and also its parts. After calculating the mass of each and every material, the corresponding carbon emission was found by determining the equivalent amount of CO2 with the help of the SimaPro software.

Measurement of VOCs VOCs measurement was done by using the VOC Environmental Meter (PCE-VOC) in the footwear industry environment. The values were displayed in ppm.

VOCs Measurement Data Analysis The measurement data for the carbon footprint and VOCs emissions was processed and analysed in the Microsoft Excel computer program. Each value was taken several times and then the average was determined.

RESULTS AND DISCUSSION The carbon footprint and VOCs emissions values were taken from 10 different factories. Based on our findings the average normalized values are shown in Table 1, 2, 3 and 4 as a calculated average from those 10 selected factories.

A breakdown of shoes’ mass by part and by material is illustrated in Table 1 and 2. The paper in the packaging, upper leather, lining leather (pig), fabrics and the interlining used in shoes’ upper part, EVA in the midsole, and PU in the outsole made up the majority (62.2%) of shoes’ mass. The breakdown of materials is also shown in Figure 1. Calculating the quantity of materials with their respective emissions’ factors [7], it was determined that 9.174979 kg CO2‐eq. of greenhouse gases was emitted in the material-processing phase of the shoemaking process.

Shoe designers should focus on upper and sock lining materials, specifically textiles, polyester, and polyurethane, in order to reduce the materials’ impact.

Table 1. Breakdown of materials of a reference shoe Footwear Manufacturing

Quantity (per pair)

Materials

Mass (g)

Cow leather

135

Lining leather (pig)

90

Fabrics and interlining (textile)

44

Glue

167

EVA

22

Solvent

50

Paper

372

Lace

15

Sole (PU)

268

Water per pair, litre

334

Energy per pair, MJ

3.31

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MAHMUD Y, et al. Assessment of the Carbon Footprint and VOCs Emissions … TLR 4 (1) 2021 23-29.

The following Table 2 visualizes the results obtained through our research, the database of the SimaPro software.

Table 2. Footprint of materials for one pair of shoes Processes

Materials

Quantity (kg)

Textile production

Fabric and interlining

Rubber production

Footprints for one pair of shoes Energy (MJ)

Water (l)

CO2 eq. (kg)

0.03721

1.55623

2.47092

1.15420

Sole

0.38010

0.76028

2.44021

0.98013

EVA

0.02486

0.02275

0.09765

0.04987

Laces

0.01309

0.06989

0.39428

0.06798

Pig leather production

Pig leather

0.09298

5.90E-05

n.d.

0.00198

Cow leather production

Cow leather

0.13987

0.18185

1.17219

0.01730

Plastic production

Glue 0.18001 n.d. n.d.

0.13445 Chemicals production UL-ISALM MR, et Solvents al. Assessment of the Carbon Footprint and VOCs Emissions … TLR 0 (0) 2020 00-00.

0.04899 0.02399 0.07985 0.11586 Paper production

Paper

Paper production Shoe manufacturing

Paper

Shoe manufacturing

12.13855

0.26985 1 pair of shoes 1 pair of shoes

Transport 15 km (incl. fuel Transport cons.) 15 km (incl. fuel cons.)

Total

0.26985

1.67823

0.80129

12.13855 3.25101

1.67823 0.03712

0.801295.85109

3.25101

0.03712

5.85109

2.17E-04

1.22E-03

6.29E-04

2.17E-04 18.004826

Total

18.004826

1.22E-03 8.37167

8.37167

6.29E-04

9.174979

9.174979

Figure 1. Materials massper per pair of shoes Figure 1. Materialsvs. vs. mass pair of shoes

Carbon Footprint

Carbon Footprint

In Table 2, the calculations were based on the weight of each material. The total energy footprint is

In Table 2,18.004826 the calculati werewater basedfootprint on the weight of each The carbon total energy footprint is 18.004826 MJ; ons the total is 8.37167 litres;material. and the total footprint is 9.174979 MJ; the total water footprint is 8.37167 litres; and the total carbon footprint is 9.174979 kg CO eq. The kg CO2 eq. The highest impact in the energy footprint is in the production of paper with a 12.13 MJ,2 highest impact in the energy footprint is in the production of paper with a 12.13 MJ, which is invested into the which is invested into the production of the box and the paper packaging. The footprint for one pair production of the box and the paper packaging. The footprint for one pair of shoes is illustrated in Figure 2. of shoes is illustrated in Figure 2.

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kg CO2 eq. The highest impact in the energy footprint is in the production of paper with a 12.13 MJ, which is invested into the production of the box and the paper packaging. The footprint for one pair MAHMUD Y, et al. Assessment of the Carbon Footprint and VOCs Emissions … TLR 4 (1) 2021 23-29. of shoes is illustrated in Figure 2.

Figure 2. Footprintof ofmaterials materials for pairpair of shoes Figure 2. Footprint forone one of shoes

The smallest energy footprint is in the production of pig leather, 5.90 E-05 MJ. The two largest water footprints are in the production of the textile fabric and the interlining (2.47 litres) and in the rubber production, needed for making the soles out of PU (2.44 litres). The total carbon footprint is 9.17 kg of carbon dioxide equivalents. The greatest impact in the carbon footprint is in the production of shoe manufacturing with a 5.85 kg of CO2 equivalents.

Water and Energy Resource Used The water and the energy footprint is showed above with the carbon footprint results. Moreover, the general data used can be seen in Table 3.

Table 3. Normalized values of water and energy for one pair of shoes Energy use per pair

3.31 MJ

Water use per pair

0.036 l

Incineration

20-50%

Reuse rate

3-7%

Repair rate

2-6%

The energy required to produce one pair of shoes was determined to be 3.24 MJ and the water footprint was 0.036 L. The incineration rate is 20-50%. The reuse rate is 3-7%. The repair rate is 2-6%.

VOCs Emissions The total VOCs consumption for footwear varies depending on the type of footwear being produced. In our study, fashion shoes have a solvent consumption of 36.5 g/pair.

For fashion shoes (see Table 5) the process of sole assembly (joining the “fashion materials”) generates the highest amount of solvents emissions in the whole shoemaking process (>40%). The finishing of the shoes – colouring, brilliant varnishing etc. – also generates high emissions (~20%). VOCs emissions caused by the process of making fashion shoes is illustrated in Figure 3.

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MAHMUD Y, et al. Assessment of the Carbon Footprint and VOCs Emissions … TLR 4 (1) 2021 23-29.

Table 5. Breakdown of materials of a reference shoe Operation

VOCs Input (g)

VOCs Input (%)

Stitching

2.30

6.30

Homogenizing

0.30

0.82

Heal Seat

5.10

14.00

Preparing

0.10

0.27

Sole Preparation

4.50

12.32

Sole Assembly

15.30 15.30 1.60

41.20

UL-ISALM MR, et al. Assessment of the Carbon Footprint and VOCs Emissions … TLR 0 (0) 2020 00-00.

Sole Assembly Printing Finishing Cleaning Total

Printing Finishing Cleaning Total

1.60 6.80 6.80 0.50 0.50 36.50 36.50

4.38 18.63 1.36 100.00

41.20 4.38 18.63 1.36 100.00

Figure fashion shoe shoe Figure3.3.Typical TypicalVOCs VOCsinput input for for aa fashion

CONCLUSION CONCLUSION The dangers of VOCs were identi fied some years ago ago and and sufficient concern was raised in order to ensure The dangers of VOCs were identified some years sufficient concern was raised in order to the development of the legislation. The carbon footprint and VOCs can aggravate the condition of both the ensure the development of the legislation. The carbon footprint and VOCs can aggravate the environment and human beings. This study provides the quantitative information about the VOCs and the condition of both environment and footprint human beings. study the MJ, quantitative carbon footprint, such the as that the total energy for one This pair of shoesprovides is 18.004826 the water information aboutlitres the and VOCsthe and the carbon footprint, suchkgasofthat total energy one equivalents.

For footprint one pair offor fashion footprint is 8.37167 carbon footprint is 9.174979 CO2the shoes, are around 36.5 g/pair on average.

But these on some sub-factors, suchisas pair VOCs of shoes is 18.004826 MJ, the water footprint is factors 8.37167depend litres and the carbon footprint whether the VOCs arise from adhesives, finishing products or cleaners etc. If the amount of these factors 9.174979 kg of CO2 equivalents. For one pair of fashion shoes, VOCs are around 36.5 g/pair on average. exceeds the standard value, then it can adversely affect our society. Once the hazardous elements and Butrisks these factors depend onfurther some steps sub-factors, such in asorder whether the VOCs arisehazardous from adhesives, their have been identi fied, can be taken to either eliminate materials finishing products cleaners etc. substi If the tutes. amount these factors exceeds the standard value, from then the it and processes or findor less hazardous Theofnext step is then to minimize the emissions factories into theaffect environment by suitable means. can adversely our society.

Once the hazardous elements and their risks have been identified,

further steps can be taken in order to either eliminate hazardous materials and processes or find less hazardous substitutes. The next step is then to minimize the emissions from the factories into the 28 www.textile-leather.com environment by suitable means.

MAHMUD Y, et al. Assessment of the Carbon Footprint and VOCs Emissions … TLR 4 (1) 2021 23-29.

Acknowledgements The authors wish to acknowledge the Institute of Leather Engineering & Technology (ILET), University of Dhaka for instrumental and managerial support. This research was supported by the Institute of Leather Engineering & Technology (ILET), University of Dhaka. We thank our colleagues from the Leather Goods and Footwear Manufacturers and Exporters Association of Bangladesh (LGFMEAB) who provided the insight and the expertise that greatly assisted the research, although they may not agree with all of the interpretations of this paper.

REFERENCES [1] Cheah L, Duque Ciceri N, Olivetti E, Matsumura S, Forterre D, Roth R, Kirchain R. Manufacturing-focused emissions reductions in footwear production. Journal of Cleaner Production. 2013; 44:18–29. https:// doi.org/10.1016/j.jclepro.2012.11.037 [2] Gangopadhyay S, Ara T, Dev S, Ghoshal G, Das T. An Occupational Health Study of the Footwear Manufacturing Workers of Kolkata, India. Studies on Ethno Medicine. 2011; 5(1):11–15. https://doi. org/10.1080/09735070.2011.11886386 [3] Al Mamun MRU, Howlader S, Yeahyea HB. Leather Industry of Bangladesh: A new hope for export diversification Editorial Overview. Emerging Credit Rating Limited, Dhaka; Bangladesh 2016.

[4] Nur MS. A Study on Advantages of Sourcing Apparel from Bangladesh. Louisiana State University and Agricultural and Mechanical College; 2016. 69 [5] Munoz ZR. Water, energy and carbon footprints of a pair of leather shoes. Division of Industrial Ecology, KTH Royal Institute of Technology, Stockholm, Sweden; 2013. 38 [6] Deb AK, Chowdhury M, Ahammed F, Azam B, Hossain I. Workers’ Health and Workplace Condition Evaluation (WCE) Of the Footwear Industries in Bangladesh Workers’ Health and Workplace Condition Evaluation (WCE) Of the Footwear Industries in Bangladesh. Journal of Environmental Science, Toxicology and Food Technology. 2018; 12(8):7-13. 10.9790/2402-1208010713.

[7] Vallero D. Fundamentals of Air Pollution. 5th edition. Waltham, USA: Elsevier; 2014.

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HOSSAIN MD, AZAM FAB, CHOWDHURY M. Quality Assesment of Shoe Leather… TLR 4 (1) 2021 30-37.

Quality Assessment of Shoe Leather Based on the Properties of Strength and Comfort, Collected from Different Footwear and Leather Industries in Bangladesh Md. Delwar HOSSAIN, Forhad Ahammed Bin AZAM, Manjushree CHOWDHURY* Institute of Leather Engineering and Technology, University of Dhaka, Bangladesh *manjushreechow@gmail.com Article UDC 685.341.355.1:685.34.017 DOI: 10.31881/TLR.2020.20 Received 7 October 2020; Accepted 22 December 2020; Published Online 22 December 2020; Published 2 March 2021

ABSTRACT Based on the environmental condition, a shoe manufactured with different suitable materials has to provide optimum comfort and strength features by using high-quality leather parts. The aim of the study is to evaluate the quality of the shoe upper leather in Bangladesh. Ten different types of shoe leather, made from cow hides and goat skins, were collected from different footwear and leather industries in Bangladesh. The research was carried out by using approved methods of analysis as per the International Union of the Society of Leather Technologists and Chemists’ official methods for physical and chemical analysis. Physical and chemical properties, which were studied three times for each of the samples, were tensile strength, percentage of elongation, tearing strength, grain crack resistance, water vapor permeability, flexing endurance, scuff resistance, perspiration fastness, color rub fastness, bond strength of the finish film, the pH, moisture content, chromic oxide content and fat content, respectively. From the study, it has been revealed that samples 02 and 08 were completely unacceptable, samples 04, 05 and 07 were moderately acceptable, and the remaining samples, 01, 03, 06, 09 and 10, were strongly acceptable on the basis of the ISO standard for shoe leather. To get the better quality, the above mentioned tests should be improved, thus the demand and the value of shoe leather, as well as footwear, will be increased and the rejection rate will be decreased gradually.

KEYWORDS Footwear, Shoe’s upper part, Strength, Comfort properties, Quality evaluation

INTRODUCTION Shoes are an essential item of apparel used in our everyday life. Various types of footwear have been developed, considering different conditions of life and work [1]. There are significant differences between shoes used in our daily lives and those that are manufactured for industrial, agricultural, military, athletic and artistic purposes [2-4]. In footwear manufacturing, there are various types of materials, such as leather, synthetics, different fabrics and polymers, used for the upper part of the shoe. The quality of footwear mostly depends on shoe leather. These leathers are affected by foot movements and must protect the foot from outer impacts [5]. Figure 1 shows all the different parts of the shoe’s upper part, where toe cap and vamp portion are the most valuable parts of the shoe’s upper part and require greater strength with comparison to other parts. Physical properties of shoe leather should be high if quality is desired. Various 30 www.textile-leather.com

HOSSAIN MD, AZAM FAB, CHOWDHURY M. Quality Assesment of Shoe Leather… TLR 4 (1) 2021 30-37.

physical, chemical and fastness properties are required from leather products depending on their field of use [6]. To assess the strength properties of upper materials, overall strength in the parallel direction to the leather surface, number of good fiber strength, fiber strength in the weak area, and the overall strength of the leather should be measured. A pair of shoes with good comfort properties is important to the health of the feet and the whole body. With the growing concern for our health, better comfort properties from the wearing of the shoes are expected. Comfort properties of leather shoes mainly point to air permeability, water vapor permeability, flexibility, heat preservation and antimicrobial ability [7]. In the early 70’s, comfort was defined as a lack of discomfort [8]. On the other hand, comfort can be defined as a feeling of relaxation and well-being [9]. The upper material of the shoes should endure proper flexing. The bending and flexion properties of leather materials, which will be used in shoe manufacturing, are required to be high and compatible. Therefore, leathers with poor flexibility values show folding and breaking parts [10].

Besides that, the upper material of the shoes should be permeable to perspiration, otherwise the foot will be in a wet condition, which facilitates bacterial and fungal growth and produces bad odor inside the shoe.

Footwear comfort and discomfort was found to embed positive and negative sensations of the leather.

Leathers used both in garment and shoe production, should have water vapor and air permeability characteristics to some extent. High perspiration fastness value is desired by the shoe manufacturers. In a resting state one foot excretes 72 ml of sweat per day [1]. The sweat shows slightly acidic character when it is fresh and the pH of the sweat is changed in a range of 5.2- 7.0. The acidic character of the fresh sweat is slightly M, to AZAM CHOWDHURY M.the Quality Shoe 0 (0) 2020 00-00. changed intoHOSSAIN alkalic due the FAB, urease enzyme and pH isAssesment increasedofup to 9Leather…

[11]. TheTLR finishing step is the final make-up of the leather. Most finishing mixtures are compatible with the base color. The quality of the finishing property is determined by dry/wet rub fastness, light fastness and the test for the adhesion of the sustain world market, can Bangladesh has to attention to the quality and comfort cost. Theseems aim ofto finish; andthe these fastnesses be increased bygive the special use of proper chemicals.

Footwear bethe governed factors, es of upper material of a shoe shoe style, shoe study isbytomany evaluate the including different properti properties of the shoe leathers collected from[12], randomly selected fittings [13-15] and psychological factors [16-17], all of which contribute towards imparting the sensation. footwear and leather industries in Bangladesh. From the previous research [1,5,11,19], it has been Water and air vapor permeability have played an important role to determine the hygienic property of the found that there were several studies about either strength properties or comfort properties of shoe shoe’s upper part. leather, while overall fiperformance of shoe depends oncountry both strength comfort properties.

Bangladesh has already lled up the conditi onleather to be a developing [18]. In and future, Bangladesh has to pay highbest tax of forour exporti ng in thethere footwear wellfew as the leather sector.

To capture and sustain the world Toathe knowledge, wereasvery studies on shoe leather in Bangladesh, which are market, Bangladesh has to give special att enti on to the quality and cost.

The aim of the study is to evaluate the prerequisite for shoe manufacturing. the different properties of shoe leathers collected from randomly selected footwear and leather industries If the quality of shoe leather manufactured in Bangladesh can be improved, other countries will in Bangladesh. From the previous research [1,5,11,19], it has been found that there were several studies showeither interest to import better quality shoe leatheresfrom thisleather, country.

So, both strength and comfort about strength properti es or comfort properti of shoe while overall performance of shoe

properties of shoe leather are required for a better image and the future of Bangladesh.

Figure 1. Different parts of the shoe Figure 1. Different parts of the shoe

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BACKGROUND OF DIFFERENT PROPERTIES OF SHOE LEATHER

HOSSAIN MD, AZAM FAB, CHOWDHURY M. Quality Assesment of Shoe Leather… TLR 4 (1) 2021 30-37.

leather depends on both strength and comfort properties. To the best of our knowledge, there were very few studies on shoe leather in Bangladesh, which are the prerequisite for shoe manufacturing.

If the quality of shoe leather manufactured in Bangladesh can be improved, other countries will show interest to import better quality shoe leather from this country. So, both strength and comfort properties of shoe leather are required for a better image and the future of Bangladesh.

BACKGROUND OF DIFFERENT PROPERTIES OF SHOE LEATHER Strength Properties Tensile strength is the maximum tensile stress recorded in extending a test piece to the breaking point [18].

Tensile strength is a good area for checking whether the shoe leather has sufficient structural resistance [19-20]. Tensile strength depends on the moisture and fat contents of the leather. When moisture content goes down due to long storage or due to evaporation, the leather shows lower tensile strength up to a certain limit. A similar result is obtained for fat content [21]. In tensile strength, the strength of the leather is measured in a direction parallel to the surface of the leather, whereas in stitch tearing strength, the strength is measured at the right angle to the leather surface. The strength of the fibers is determined by the Bauman tearing strength, in which leather thickness will be one or more than one millimeter. To assess the quality of the leather, it is essential to evaluate tearing strength in the weakest area. This is done by testing the tongue tearing strength. Grain crack strength (Lastometer) test is mandatory for shoe leather. Grain crack strength indicates whether the leather will or won’t withstand a lasting operation. Strength properties of the leather vary depending whether they are measured parallel to the backbone or perpendicular to the backbone. So the strength of the leather indicates the average of the two above strengths [22].

Comfort Properties Flexing endurance test is nothing but a simple folding of a leather specimen several times with grain side out with the help of a machine. Any change due to such folding indicates poor flexing endurance [22]. When leather is flexed or folded several times as in the vamp portion of the shoes, the free grease is pushed away from the flexed region, so the leather cracks there or wrinkles develop. Water vapor permeability as well as perspiration fastness is the mandatory test for shoe leather, though both of the tests are more potential for shoe lining. The rate of penetration of water vapor through the leather specimen is mainly governed by the vapor pressure difference between the two sides of the leather specimen [11]. Liquid water penetrates into upper leather due to its emptiness but this emptiness in upper leather is essential for its flexibility, good feel, water and air vapor permeability; therefore, upper leathers should be made more waterproof by affecting their emptiness [23]. Scuffing is actually a milder form of abrasion caused due to an impact or sudden hitting of the leather surface against an object. During walking, the toes of the shoes very often get suddenly hit by pebbles, some stones and other sharp objects. Shoe leather should therefore be resistant to such scuffing at least up to a reasonable extent. Color-rub fastness test is carried out not only to measure the resistance of the finish film to the transfer of color, but also assess many other properties of the finish film adhered to the leather surface, while bond strength test actually measures the bond strength between the leather and the finish film [22].

32 www.textile-leather.com

HOSSAIN MD, AZAM FAB, CHOWDHURY M. Quality Assesment of Shoe Leather… TLR 4 (1) 2021 30-37.

MATERIALS AND METHODS Sample collection In Bangladesh, the leather sector is leading as the second most-earning export sector after ready-made garments. Ten shoe leather samples were collected from randomly selected different leading and prestigious footwear and leather industries which mainly reflect the economy in the leather sector of Bangladesh around Dhaka city. The thicknesses of test samples was measured by using SATRA- Thickness gauge. Table 1 shows the test samples’ thickness in mm and their types.

Table 1. Materials Sample No.

Thickness (mm)

Types of leather

01

1.25

Cow, Aniline leather

02

1.11

Goat, Aniline leather

03

1.23

Cow, Aniline leather

04

1.20

Cow, Semi Aniline leather

05

1.15

Cow, Semi Aniline leather

06

1.24

Cow, Aniline leather

07

1.23

Cow, Semi Aniline leather

08

1.10

Goat, Aniline leather

09

1.31

Cow, Aniline leather

10

1.33

Cow, Aniline leather

Chemicals Various chemicals (E. Mark Germany) of analytical grade were used for physical and chemical tests. The chemicals used in different physical and chemical tests are silica gel and PU adhesives, nitric acid (70% concentrate), sulfuric acid (98% concentrate), di-chloro methane, orthophosphoric acid (90% concentrate), potassium iodide, sodium thiosulphate, 0.1 N standard volumetric solutions, and the starch indicator.

Methods Some physical and chemical tests (for strength and comfort properties) were carried out to evaluate the quality of shoe leather. At first, the samples were conditioned and then the test procedure was done. All of the test samples were conditioned at 27±2ᵒC, 65±2% of humidity for 24 hours. Sharp press knives were used for cutting the sample. All of the experiments were performed at least three times to minimize the analytical error.

Table 2. Tests conducted and the methods of analysis Name of the experiments

Method of analysis

Tools and equipment

Determination of the thickness of shoe leather

IUP-4/ 1996

SATRA thickness gauge

Sampling of shoe leather

IUP-2/2001

Determination of tensile strength and the percentage of elongation

IUP-6/2001

Tensile testing machine (STD-172, serial no.: 9167, England).

Determination of stitch tearing strength

SATRA-PM-5

Tensile testing machine (STD-172, serial no.: 9167, England).

Determination of the tongue tear strength

IUP-8

Tensile testing machine (STD-172, serial no.: 9167, England).

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HOSSAIN MD, AZAM FAB, CHOWDHURY M. Quality Assesment of Shoe Leather… TLR 4 (1) 2021 30-37.

Determination of the Bauman tear strength

IUP-8

Tensile testing machine (STD-172, serial no.: 9167, England).

Determination of distension and strength of grain by the Ball burst test

IUP-09

Lastometer (STM-104)

Determination of flexing endurance

IUP-20/2001

Bally flexometer (model: 2396)

Determination of dry color rub fastness

SATRA-PM-08

Rub fastness tester (model: STM461), cotton wool and a gray scale

Determination of water vapor permeability

SATRA PM-172

Water vapor permeability machine (model: STM-473, SATRA, UK)

Determination of water-proofness

SATRA-PM-34

Water-proofness tester (model: STM-106D, SATRA, UK)

Determination of scuff resistance

SATRA-PM 140

Ford abrasion tester (STM423, serial no.: B789-199).

Determination of perspiration fastness

BSEN-ISO-105

Oven for the perspirometer apparatus (model: 290, England) and a gray scale

Determination of bond strength of the finish film

SATRA AM-08

Tester of the adhesion of the finish film (model: STD172, serial no.: C-643,2001).

Determination of the pH

SLC 2/3

A pH meter with a glass electrode

Determination of moisture content

SLC 113

Filter paper thimbles of a suitable size and manufacture, oven

Determination of chromic oxide content

SLC 8 (IUC; BS 1309; 8)

Filter paper thimbles of a suitable size and manufacture, oven

Determination of fat content

SLC 4 (IUC; BS 1309; 4)

Soxhlet apparatus, filter paper thimbles of a suitable size and manufacture, oven

RESULTS AND DISCUSSION All of the analysis results of the tested samples were enlisted in the tables and were given in average value.

Strength Properties of the Sample The testing of strength properties of shoe leather was carried out by using standard methods. Table 3 shows the results of different strength properties tests.

Table 3. Strength properties of the samples Sample No.

Tensile strength (kg/cm²)

Percentage of elongation

Stitch tearing value (kg/cm)

Tongue tearing value (kg/cm)

Bauman tearing value (kg/cm)

Grain crack load (kg)

Ball bursting load (kg)

Distension (mm)

Remarks

01

280.50

36.45

86.5

37.25

45.1

20.40

27.0

7.45

Acceptable

02

195.45

37.30

78.3

29.50

29.75

15.35

18.7

7.35

Unacceptable

03

262.80

35.38

85.4

35.50

38.54

19.45

24.4

7.15

Acceptable

04

210.40

33.45

85.1

32.10

34.25

18.20

23.5

7.43

Acceptable

05

199.50

27.43

80.0

28.70

30.45

15.60

20.2

6.35

Unacceptable

06

270.30

36.15

87.5

35.45

40.90

20.00

25.7

7.43

Acceptable

07

201.65

30.83

80.1

30.35

37.43

19.10

24.3

7.20

Acceptable

08

150.50

36.00

72.5

28.54

30.00

14.50

18.5

7.50

Unacceptable

09

297.30

37.73

89.1

39.80

47.40

24.20

29.8

7.50

Acceptable

10

300.25

36.90

90.4

40.50

48.90

25.00

30.5

7.28

Acceptable

Standard value (ISO)

Min.200

30-40

80-100

Min. 30

Min. 30

Min. 16

Min. 20

Min. 7

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HOSSAIN MD, AZAM FAB, CHOWDHURY M. Quality Assesment of Shoe Leather… TLR 4 (1) 2021 30-37.

For strength properties, grain crack resistance, along with tongue tear strength test, is mandatory for shoe leathers, because grain crack strength indicates whether the leather will or will not withstand a lasting operation, whereas tongue tear strength is carried to measure the actual strength of fibers. Only the samples that could fulfill the requirements of both of those tests were acceptable and those that could not were unacceptable. According to the acceptable standard limit, samples 02, 05 and 08 were not acceptable, samples 04 and 07 were moderately acceptable, and the remaining samples were strongly acceptable.

Comfort Properties of the Samples Comfort properties play a pivotal role in footwear manufacture for making the life fashionable and comfortable. Comfort properties of the samples were evaluated by carrying out necessary tests which have been showed in Table 4.

Table 4. Comfort properties of the samples

Sample No.

Flexing Endurance Value in break pipiness scale (100000 cycles)

Color rub fastness Value in gray scale (Dry, 1024 cycles)

01

2

3/4

02

3

2

03

2

3/4

Water vapor Permeability (mg/cm²hr)

Perspiration fastness value in gray scale

Waterproofness (time in min.)

Scuff resistance (mm²)

0.375

4

33.5

<3

0.187

3

28.5

0.335

3/4

30.4

Bond Strength of the finish film (gm/cm)

Remarks

505

Acceptable

>3

275

Unacceptable

<3

400

Acceptable

04

3

3

0.245

3

31.6

<3

375

Acceptable

05

2

3/4

0.254

3/4

30.5

>3

350

Acceptable

06

2

3

0.279

4

32.4

<3

405

Acceptable

07

2

4/5

0.455

3

28.1

<3

575

Acceptable

08

3

3

0.193

2

28.9

>3

310

Unacceptable

09

1

4

0.257

4

35.4

<3

725

Acceptable

10

1

5

0.360

4/5

31.5

<3

625

Acceptable

Standard value (ISO)

1-2

5-3

Min. 0.2

5-3

Min. 30

Less than 3 mm2

Min. 200

For comfort properties, flexing endurance, color rub fastness, water vapor permeability and water-proofness tests are mandatory, although water vapor permeability is more important for shoe lining in comparison to the upper part. Only the samples which could meet the requirements in those tests were acceptable and those that could not were unacceptable. On the basis of the acceptable limit, samples 02 and 08 were not acceptable, samples 04, 05 and 07 were moderately acceptable and the remaining samples were strongly acceptable.

Chemical Properties The presence of an excessive amount of chemicals in shoe leather makes the foot unhygienic and uncomfortable. On the other hand, an insuficient amount of chemicals hampers the performance. Table 5 shows the result of the tests of different chemical properties.

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HOSSAIN MD, AZAM FAB, CHOWDHURY M. Quality Assesment of Shoe Leather… TLR 4 (1) 2021 30-37.

Table 5. Chemical properties of the samples Percentage of moisture

Chromic oxide amount (%)

Fat content amount (%)

Sample No.

pH value

Remarks

01

4.4

10.7

3.1

7.9

Acceptable

02

4.9

12.3

5.5

9.4

Unacceptable

03

4.7

9.5

3.3

6.3

Acceptable

04

4.3

13.0

4.5

7.8

Acceptable

05

4.0

12.5

5.1

7.2

Acceptable

06

4.1

11.5

4.0

6.9

Acceptable

07

3.8

13.5

5.0

7.1

Acceptable

08

3.0

14.5

5.7

8.8

Unacceptable

09

5.0

10.6

3.2

6.5

Acceptable

10

4.5

9.9

3.5

7

Acceptable

Standard value (ISO)

≥3.5

10-12

Min. 2.5

6-8

From the experiment mentioned in table 5, it has been seen that except sample 02 and 08, the remaining samples could perform at the acceptable limit of most of the tests. According to the standard limit, samples 02 and 08 were not acceptable and the remaining samples were strongly acceptable.

CONCLUSION The choice of footwear material significantly influences foot comfort. In this study, leather samples were analyzed to show how physical and chemical properties of upper leathers can differ appreciably one from another. From the study, it has been seen that sample 02 and 08 were not acceptable, sample 04, 05 and 07 were partially acceptable and the remaining samples were strongly acceptable as shoe leather based on the mandatory tests where comfort properties are more preferable in comparison to strength properties. To maintain better strength as well as comfort quality, tensile strength and the percentage of elongation, tearing strength, grain crack resistance, water vapor permeability, flexing endurance, scuff resistance, perspiration fastness, color rub fastness, bond strength of the finish film, the pH, moisture content, chromic oxide content and fat content should be improved. If the quality of shoe leather can be improved prior to the manufacturing of shoes, the demand and value for shoe leather as well as footwear will be increased and the rejection rate decreased gradually and, thus, the overall production cost will be low.

Acknowledgements The authors are grateful to the Institute of Leather Engineering and Technology (ILET), University of Dhaka, Bangladesh.

REFERENCES [1] Bitlisli B, AdıgüzelZengin A, Yeldiyar G, Kairanbekov G, Küçükakın E. Upper Leathers in Shoe Manufacturing.

Journal of Industrial Technology and Engineering. 2013; 2(07): 37 – 41.

[2] Bitlisli BO, Sari O. Problems Stemming from Upper Leathers in Military Shoes and Boots and Suggested Solutions. Infantry 2000 Symposium CD, Tuzla Infantry Cadet School Command. Istanbul. 2000.

[3] Bitlisli BO, Karavana HA, Başaran B, Aslan A. Importance of Using Genuine Leather in Shoe Production in Terms of Foot Comfort. Journal of the Society of Leather Technologists and Chemists. 2004; 89(107):42.

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[4] Sari O, Bitlisli BO. Sole Leather Production in Turkey and Evaluation of its Quality Levels. National Shoe and Side Industry Symposium Papers, Konya Chamber of Commers. Konya. 1996; 94-106.

[5] Mehmet MM, Nilay O, Birgul K, Samet G. Determination and Mapping of Tear Load, Tensile Strength and Extension Values on Overall Area of Goatskin Leathers. ICAMS 2016 – 6th International Conference on Advanced Materials and Systems. 2016.

[6] Ork N, Ozgunay H, Mutlu MM, Ondogan Z. Comparative Determination of Physical and Fastness Properties of Garment Leathers Tanned with Various Tanning Materials for Leather Skirt Production.

Tekstil ve Konfeksiyon. 2014; 24(4):413-418.

[7] TS EN ISO 2589 Leather - Physical and mechanical tests - Determination of thickness, Turkish Standard (TSE), Ankara. 2016.

[8] Priyanka K, Shahnaz J, Kirti K. A Review on Leather Processing. International Journal of Applied Research.

2015; 1(9):977-982.

[9] Bunglavan SJ, Duttan N. Use of tannins and organic protectants of proteins in digestion of ruminants.

Journal of livestock science. 2013; 4:767-773.

[10] Gerhard J. Possible defects in leather production. p.342.

[11] Ding S, GeWeihui, LiuLijun. Testing of the permeability to water vapor of shoe upper leathers. Leather Science and Engineering. 2012;16(3):19-2413.

[12] Hertzberg HTE. The human buttock in sitting: Pressures, patterns and palliatives, American Automobile Transactions, 2004;72:39-47.

[13] Zhang LJ, Helander MG. Identifying Factors of Comfort and Discomfort in Sitting, Human Factors. 2013; 38(3):377-389.

[14] Goonetilleke RS. The Comfort-Discomfort Phase Change, International Encyclopedia of Ergonomics and Human Factors, W. Karwowski (Ed.), Taylor and Francis. 2001:389-399.

[15] Sarker MR, Deb AK, Chowdhury M, Hossain MI. Investigation and evaluation of the quality features related to comfort of casual shoes in Bangladeshi leading retail brands using physical and chemical standard test methods. Leather and Footwear Journal. 2019, 19(1):11-20.

[16] Goonetilleke RS. Footwear Cushioning; Relating Objective and Subjective Measurements. Human Factors. 2008; 41(2):241-256.

[17] Luximon A, Goonetilleke RS, Tsui KL. A Fit Metric for Footwear Customization, Proceedings of the 2013, World Congress on Mass Customization and Personality. 2013.

[18] LE DEVELOPED COUNTRY CATEGORY: BANGLADESH PROFILE, Economic Analysis & Policy Division, Department of Economic & Social Affairs, UN. 2018.

[19] Mengstu A. Performance of Leather Uppers of Local Footwear products and the Determinants, International Journal of Advancements in Research & Technology. 2014; 3(3):26.

[20] SATRA. Testing Equipment Catalogue. 2011 [21] ESA (Ethiopian Standards Agency). The quality standards for leather and leather products, Addis Ababa, Ethiopia. 2012.

[22] Dutta SS. An introduction to the principles of physical testing of leather. 1990; 42-46,55.

[23] Shahriar A. Enhancement of Waterproofing Properties of Finished Upper Leather Produced from Bangladeshi Cow Hides, European Journal of Engineering Research and Science. 2019; 4(7):2.

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NYAKUNDI JO, OMBUI JN, MULAA FJ, WANYONYI WC. Evaluation of the Bacillus cereus Strain… TLR 4 (1) 2021 38-54.

Evaluation of the Bacillus cereus Strain 1-p Protease for the Unhairing of Goatskins during Leather Production Joseph Ondari NYAKUNDI1*, Jackson Nyarongi OMBUI1, Francis Jakim MULAA2, Wycliffe Chisutia WANYONYI3 Department of Public Health Pharmacology and Toxicology, Faculty of Veterinary Medicine, University of Nairobi, P.O. Box 30197 - 00100, Nairobi, Kenya 2 Department of Biochemistry, College of Health Sciences, University of Nairobi, P.O. Box 30197 - 00100, Nairobi, Kenya 3 Department of Physical Sciences, School of Science & Technology, University of Kabianga, P. O. Box 2030- 20200 Kericho, Kenyaa *ondarijay@gmail.com 1

Article UDC: 675.023.3:675.031.3:577.15 DOI: 10.31881/TLR.2020.18 Received 8 September 2020; Accepted 2 December 2020; Published Online 23 December 2020; Published 2 March 2021

ABSTRACT The unhairing stage of leather processing is associated with the production of significant amounts of solid and liquid wastes. The use of enzymes to replace the polluting sulphides currently used for unhairing is a viable alternative. Various proteases from different Bacillus cereus strains as well as many other bacterial strains have been used successfully for the unhairing of skins. However, no previous work has assessed the use of the crude alkaline protease extract from Bacillus cereus strain 1-p, a novel Bacillus cereus strain obtained from the shores of Lake Bogoria - a soda lake in Kenya – in the unhairing of goatskins. This study, therefore, evaluates the potential of the protease extract from the Bacillus cereus strain 1-p to unhair goatskins.

Optimum variables for unhairing using the protease were investigated. Complete unhairing was achieved within 12 hours at 27°C and pH 12 using the crude enzyme. The period and temperature required for complete unhairing were significantly lower than that of other enzymatic unhairing techniques. Compared to the leather unhaired with sulphide, the leather unhaired with the enzyme did not only show superior organoleptic properties but also recorded comparable or superior physical properties, namely tensile strength (26.94 N/mm2), percentage elongation (76.29%), tear strength (43.59 N/mm), and distension at grain crack and burst (7.9 mm and 8.2 mm respectively). The wastewater from the enzymatic unhairing process recorded a significant reduction in biochemical oxygen demand (78%), chemical oxygen demand (83%), and the wastewater volume (50%) compared to the process that uses sulphide. It was concluded that the use of the crude protease extract from the Bacillus cereus strain 1-p in unhairing goatskins is feasible.

KEYWORDS Bacillus cereus, Unhairing, Protease, Leather

INTRODUCTION Leather is a valuable prehistoric natural commodity that is being used in modern times, and plays an indispensable economic role globally. Leather and finished leather products are estimated to have a global value of about USD 100 billion annually [1]. In the year 2013, footwear made of leather accounted for approxi38 www.textile-leather.com

NYAKUNDI JO, OMBUI JN, MULAA FJ, WANYONYI WC. Evaluation of the Bacillus cereus Strain… TLR 4 (1) 2021 38-54.

mately USD 53.5 billion [2]. Despite making such substantial contributions towards economic development, the leather industry is blamed for severe environmental pollution resulting from the application of toxic agents in processing of hides and skins [3]. Leather processing entails the transformation of the biodegradable rawhide/skin into leather, a non-biodegradable product. This is through a series of processing stages that can be summarized into pre-tanning, tanning and post tanning [4,5].

The initial stages of leather processing generate 80–90% of wastes produced from tanneries [6]. Unhairing is a pre-tanning step in leather processing where toxic sulphide chemicals are used. This stage is thus associated with major environmental pollution. In the conventional unhairing technique, hides and skins are exposed to an extreme chemical treatment using lime and sodium sulphide that breaks down the hair and epidermal structures to remove them from the hide/skin [7]. As a result, this processing stage releases volumes of solid wastes in the form of broken epidermal structures and hair [8]. Additionally, this stage is responsible for air emissions that have negative effects on the environment, since some of the gases cause photochemical reactions, destruction of the ozone layer through the increase in greenhouse gases that lead to the formation of acid rain [9]. These concerns have necessitated the need for cleaner alternative technologies to eliminate the use of sulphides in the unhairing process.

Over the years, enzyme technology has made major strides in transforming several industrial processes into cleaner production systems. Enzymes have been used in food, textile, detergents and soaps, bioactive peptides, agricultural, cosmetic, beverage, pharmaceutical and leather industries, among others [10].

Microbial enzymes have been employed in tanneries for rehydration, hair removal, bating and removal of fats [7]. The application of enzymes for unhairing eliminates the use of the toxic sodium sulphide and can facilitate recovery of quality hair and fats which significantly lowers the pollution load in the effluent [10].

Enzymatic unhairing is associated with enormous benefits which include effective rehydration, scud loosening, splitting of collagen fibres, production of a smooth grain, improved soft feel making the leather pliable, improved yield, and overall reduction of the production time and pollution load [12-14].

Alkaline protease enzymes have widely been researched on, especially their application in leather processing.

The use of proteases has played a vital role in various stages of leather manufacturing from soaking to the finishing stage [15]. Many Bacillus species have been explored for protease production with high potential strains distinguished to be B. mojavensis, B. subtilis, B. licheniformis, and amyloliquefaciens [16]. Research done on the enzymatic unhairing using enzyme extracts from the Bacillus species have reported satisfactory results on their efficacy in unhairing hides and skins [14,17-25].

Various researches have reported positive results on the use of proteases extracted from different Bacillus cereus strains for industrial applications such as unhairing hides and skins during leather processing. Great advances have been documented on the potential of Bacillus cereus BM1 protease in industrial applications, whereby it has proved to be thermostable and detergent compatible and, therefore, can find commercial applications [26]. Despite the protease�s stability at an alkaline pH range of 8-12 which would be suitable for unhairing, the protease required a temperature range of 40-70°C for optimum activity, a temperature range that is too high for raw skins. A crude enzyme extract from Bacillus cereus VITSN04, whose maximum activity was reported to be at 30°C and pH 8.0, was found to be effective in unhairing of goat skins during leather processing [24]. Despite the remarkable results, this protease required 18 hours to achieve complete unhairing, a rather lengthy period in a typical production line. An extracellular protease extracted from a thermophilic Bacillus cereus strain isolated from soil demonstrated ability to completely remove glandular structures, hair and hair follicles from goatskins and cowhides at optimum conditions of pH 7.5 and temperature of 60°C [23]. The enzyme from this Bacillus cereus strain was not only active in the pH range of

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NYAKUNDI JO, OMBUI JN, MULAA FJ, WANYONYI WC. Evaluation of the Bacillus cereus Strain… TLR 4 (1) 2021 38-54.

6.0–9.0 but also at a relatively high-temperature range of 60-70°C, a temperature that would denature the raw collagen fibres in raw hides and skins during unhairing. In another study, an alkaline protease obtained from Bacillus cereus MCM B-326 was used to unhair a buffalo hide successfully at pH 7.0 and a temperature of 28 ± 2°C [27]. The protease, however, required 21 hours to achieve the complete unhairing of the hides.

This period is quite lengthy for an ideal leather production line. A protease extracted from Bacillus cereus strain SZ-4 exhibited considerable hair removal capability on bovine, hircine, porcine and ovine skins within a period of 12 hours [28]. These were appreciable results as it was further reported that the enzyme did not change the structure of the dermis. The protease extract from the Bacillus cereus strain 1-p was reported to have successfully descaled a Nile perch skin (Lates niloticus) within a period of one hour and also reported positive results in the unhairing of a bull hide [25]. The results observed from the descaling process of Nile perch fish skins were remarkable as the descaling was achieved in a short time under a pH and temperature range that can be applied to raw skins without damaging the collagen structure.

Although extensive research has been carried out on enzymatic unhairing using extracts from various bacterial strains and more so, the Bacillus cereus, no work has been published on the enzymatic unhairing of goatskins by using a crude enzyme extract from a novel Bacillus cereus strain 1-p obtained from the shores of Lake Bogoria, a soda lake in the Rift Valley, Kenya. The working hypothesis is that the crude alkaline protease extracted from Bacillus cereus strain 1-p has the potential to unhair goatskins that would eliminate the use of sodium sulphide during leather processing. This is aimed at finding a viable alternative to the toxic chemicals used in the unhairing stage of leather processing, which would make leather-making cleaner and translate to a more sustainable industry.

MATERIALS AND METHODS Materials Wet salted goatskins were purchased from a local slaughterhouse in Nairobi, Kenya. Tanning and laboratory chemicals were acquired locally, while the isolated bacteria were cultured and the enzyme extracted at the Biochemistry Laboratory, University of Nairobi. The chemicals used in this study in the laboratory and tannery were of analytical and commercial grade. The crude protease was prepared from a Bacillus cereus bacteria, strain 1-p, which had previously been isolated, cultured and identified using the analysis of 16S r DNA sequencing method [25]. The crude protease from this bacterial strain was studied in this work following the positive results reported from its use in descaling of Nile perch skins [25].

Enzyme preparation The enzyme was prepared at optimum conditions as described in a previous method [25]. A 3-litre medium was prepared with the following components: magnesium sulphate (MgSO4.7H2O), calcium chloride (CaCl2), urea, yeast, casein, glucose and distilled water. The pH was adjusted to 11.5 and left to rest for two hours for pH stabilization before sterilization of the media and the flasks to be used. An overnight bacterium seed culture (Bacillus cereus strain 1-p) in sterile distilled water was inoculated into the 3-litre medium setup in a bioreactor (Bioengineering RALF) set at 150 rpm, pH 11.5 and 45˚ C and incubated for 72 hours. The culture-medium was then obtained and centrifuged at 12,000 revolutions per minute for fifteen minutes to extract the supernatant. The supernatant was recovered and stored in covered flasks at 4°C awaiting use in the unhairing of goatskins.

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Enzyme assay The crude protease activity was investigated under optimized variables (pH 11 and 45°C) as described by Wanyonyi et al. (2015) following a modification of their method. The activity was determined using casein as the substrate at an alkaline pH. 0.1 ml of the crude enzyme was incubated with 0.1 ml of 1% w/v casein in the buffer-Tris-HCl (0.2 M, pH 9.0) at 45°C for 10 min. After the completion of the incubation, the reaction was terminated by addition of 4 ml of chilled trichloroacetic acid and placed on ice for 20 minutes to facilitate precipitation of insoluble proteins. The mixture was subsequently centrifuged for 10 minutes. 5 ml of 0.4 M sodium carbonate and 1 ml of diluted Folin-Ciocalteu reagent was added into the supernatant and incubated for 30 minutes. The absorbance was measured against a blank at 660 nm using a UV-spectrophotometer. One unit of the crude protease activity (U) was described as 1 μg of tyrosine liberated per minute per ml under standard assay conditions.

Optimization of unhairing Factors affecting the unhairing of goatskins using the crude alkaline protease were studied and optimized to achieve maximum unhairing. The effect of temperature, pH and enzyme dilution was evaluated by dipping goatskin pieces in the crude enzyme and examining the extent of hair removal periodically. Three goatskins were cut into test pieces measuring 10x10 cm, which were washed and soaked in clean water for 2 hours in order to be rid of salt and dirt. The goatskin pieces were dipped in flasks with the 250 ml crude protease (0.45 U/ml) at 25°C and a pH range of pH 2 to 13 to assess the effect of pH on unhairing. A negative control experiment was also run in flasks under similar conditions but 250 ml of distilled water was used in place of the crude enzyme. The removed hair was weighed and expressed as a percentage against the total hair recovered after the complete unhairing. The percentage was established as per the area without hair compared to the test piece’s total area. A complete hair removal was treated as 100% while no hair removal was 0%.

The flasks, covered with cotton wool and aluminium foil, were shaken at intervals of 10 min. Gentle scrubbing using a blunt piece of wood was done to assess the ease of hair removal after every hour.

Goatskin pieces were dipped in flasks with 250 ml of crude protease (0.45 U/ml) at pH 12, within a temperature margin of 25°C - 35°C in order to study the effect of temperature on the unhairing. Similarly, a negative control experiment with 250 ml of distilled water in place of the crude enzyme at pH 12 was run within the same temperature range. The flasks, covered with cotton wool and aluminium foil, were shaken at intervals of 10 minutes and the ease of hair removal was determined after every hour.

Other goatskin test pieces were dipped in flasks with the crude protease diluted in different proportions; 100% (250 ml of crude enzyme – 0.45 U/ml), 80% (200 ml of crude enzyme – 0.45 U/ml, diluted with 50 ml of distilled water), 60% (150 ml of crude enzyme – 0.45 U/ml, diluted with 100 ml of distilled water), 40% (100 ml crude enzyme – 0.45 U/ml, diluted with 150 ml of distilled water), 20% (50 ml of crude enzyme – 0.45 U/ml, diluted with 200 ml of distilled water) and 0% (250 ml of distilled water), all adjusted to pH 12 to investigate the impact of enzyme dilution on unhairing. The flasks were observed at 27°C to allow the enzyme activity to take place. The ease of hair removal was determined at intervals of one hour.

Enzymatic leather processing Once the unhairing conditions had been optimized, the unhairing of full goat skins was done with the crude alkaline protease at the optimized conditions at a local tannery. Experimental tannery drums were used to process a total of nine (9) goatskins in replicates of three using the enzyme extract. A positive control

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experiment was also set up to unhair 9 goatskins using sodium sulphide, also in triplicates. All the skins were washed thoroughly and soaked for 16 hours in the presence of a 0.2% biocide, 0.1% wetting agent and 0.5% soda ash before the start of the unhairing process. The amount of all the chemicals used was calculated as a percentage of raw weight. A complete unhairing in the experimental group was achieved using the undiluted crude protease, at the optimized pH 12 and 27°C, in 12 hours. The pelt was gently scraped using a blunt blade to remove the hair, which was recovered, washed and dried. The pelts were then limed and subsequently fleshed for the recovery of sulphide-free flesh and fats. Similarly, the positive control group was conventionally unhaired using the lime-sulphide system and fleshed. The subsequent pre-tanning, tanning and post-tanning stages were carried out in similar standard treatments for the sulphide- unhaired and the enzyme-unhaired goatskins. Notably, the experimental group was not subjected to the bating process after deliming as the pelts were clean and well opened up, unlike the control group. The chrome-tanned leathers were processed to crust leather as per a standard procedure.

Organoleptic examination and physical tests of the processed leather The enzyme-unhaired leathers were examined for visual and physical properties and compared to the lime–sulphide unhaired leathers. Various organoleptic properties that include appearance, softness, fullness, wrinkles, colour intensity and uniformity of the enzyme- unhaired and the sulphide-unhaired leathers were examined visually and through touch. They were then rated from 0 to 10 points for every examined parameter by three experienced leather technologists with higher points representing a superior quality.

Leather samples for physical testing were acquired through a standard sampling procedure as stipulated by the ISO 2418:2002 standard [29]. Eighteen (18) pieces of the enzyme-unhaired goatskin leathers were cut by applying the standard dumbbell-shaped press knife to the grain surface. Nine (9) test pieces were obtained with the longer side parallel to the backline and nine (9) with the longer edge perpendicular to the backbone.

These test samples were conditioned in a standard atmosphere and standard conditions; at the temperature of 23 ± 2°C and the humidity of 50 ± 5% for 48 hours as specified by the ISO 2419:2002 standard before testing [30]. The physical tests, such as tensile strength, tear strength and grain distension were tested as per the International Union for Physical testing for leather (IUP) methods. Tensile strength and elongation were tested in line with the ISO 3376:2002 standard [31]. The jaws of the tensile testing instrument were set apart and the samples secured in-between, aligning the jaw clamps with the midline. The machine was run and the jaws began to separate, stretching the test piece until it broke and the load recorded. The tear strength of the leather samples was measured by the Instron testing machine following the standard test method ISO3377-2:2002 [32]. A notched sample was clumped between the machine jaws. Upon the running of the machine, the jaws separated until the test piece tore and the load recorded. The strength of the grain was tested as per the standard ISO 3379:2015 [33]. A disk-shaped test piece was distended by pushing through the flesh side and observing the grain surface for incipient cracking and bursting and subsequently recorded as the distension at grain crack and distension at grain burst respectively.

Analysis of resultant liquor The resultant wastewaters from the control (sulphide unhairing) and the experimental (enzymatic unhairing) groups were obtained after the unhairing stage and analyzed for biochemical oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS) and total suspended solids (TSS) following the standard technique [34].

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Data analysis The data were analyzed by using the IBM SPSS Statistics 20 statistical tool. The T-test analysis was done to compare the means of the physical properties of the enzyme-unhaired goatskin leathers to the conventionally processed ones to assess the statistical difference of the results obtained (Significance level; α< 0.05).

The differences were concluded to be significant when p<0.05.

RESULTS AND DISCUSSION Effect of the pH on enzymatic unhairing The crude enzyme extracted after the 72h fermentation was assayed for its proteolytic activity. It was found that the activity of the crude protease from Bacillus cereus strain 1-p was 0.45 U/ml at the optimized variables.

Hydrogen ion concentration (pH) is well known to affect the enzyme activity, because enzymes are proteins in nature, thus sensitive to changes in the pH [35]. The effect of the pH on the enzymatic unhairing of goatskins was studied at the pH range 2-13 at 25°C and the observations were summarized in Figure 1. The results showed that at a low pH (acidic), there was no hair removal throughout the observation period. Partial hair removal was first recorded at pH 12, 11, 9, 8 and pH 7 after 2, 4, 5, 5 and 6 hours respectively. Complete hair removal was only observed at pH 12 and 11 after 7 and 12 hours respectively. Negative control experiments containing distilled water in place of the crude enzyme at a pH range of 2 to 12 showed no removal, indicating that the crude protease enzyme was solely responsible for the unhairing. The observed increase in unhairing efficiency with the increase in pH can be attributed to the increased effect on ionic and hydrogen bonds of the protease, which are important to the enzyme shape and its activity [36]. The observed results correspond to the properties of alkaline enzymes previously reported to show the highest unhairing rate at pH 8 to pH 12 [23-25,37-40].

Figure 1. Effect of pH on unhairing by using the enzyme from Bacillus cereus strain 1-p

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Effect of temperature on the enzymatic unhairing Increase in temperature increases the reaction rate up to a specific temperature limit, beyond which the enzyme is denatured [41]. The effect of temperature on enzymatic unhairing of goatskins was investigated within the range of 25°C–35°C, at pH 12 using the undiluted crude protease, and the results displayed in Figure 2. The unhairing efficiency increased with an increase in the temperature. 100% hair removal was attained after 5 and 6 hours at 35°C and 33°C respectively. At 27°C and 25°C, complete unhairing was achieved after 7 hours. The negative control experiments showed no hair removal. These findings are significantly positive as hair removal was achieved in an acceptable temperature range for the raw hides and skins in a significantly short period. High temperatures are avoided in the early stages of leather processing because the shrinkage/denaturation temperature for raw skins is approximately 65°C around neutral pH while at high pH the skin’s shrinkage temperature reduces to 50°C or less; it is thus recommended that the temperature for the soaking, unhairing and liming of skins must be limited to less than 30°C [42]. These observations showed a significant potential of the protease enzyme from the Bacillus cereus strain 1-p to be used for unhairing. These results are better than those reported of other microbial enzymatic unhairing techniques that required significantly higher temperature ranges to achieve complete hair removal [14,17,23].

Figure 2. Effect of temperature on unhairing by using the enzyme from Bacillus cereus strain 1-p

Effect of the enzyme activity on the unhairing activity Enzyme concentration affects the rate of enzyme activity by altering the number of enzyme molecules present. The effect of the enzyme dilution on unhairing of goatskins was determined at 27°C and pH 12 using proportions of the crude enzyme diluted using distilled water and the results presented in Figure 3.

The results show that the protease unhairing efficiency decreased with the increase in the crude enzyme dilution. Complete hair removal was first observed in the ratio 100:0 after 7 hours while the ratios 80:20 and 60:40 took 9 hours and 10 hours respectively to achieve complete unhairing. This can be ascribed to the fact that the enzyme activity is highly dependent on its molecular concentration, which means that a high enzyme concentration translates to high enzyme activity [43]. Although various factors affecting the enzymatic unhairing have been investigated and are well established, the effect of the enzyme dilution has not been extensively studied and documented. Nonetheless, as an increase in dilution generally lowers 44 www.textile-leather.com

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the concentration of enzyme molecules present in a specific volume, these findings correspond to those reported from the use of a protease extract from Bacillus crolab MTCC 5468 to unhair goatskins where the unhairing activity and efficiency increased with the increase in enzyme concentration, thus a complete unhairing was achieved faster [7].

Figure 3. Effect of the enzyme activity on the unhairing by using the enzyme from Bacillus cereus strain 1-p

Unhairing of full goatskins The established optimum variables were used to unhair full goatskins by using the crude protease derived from Bacillus cereus strain 1-p at a local tannery. A positive control run was set up, where goatskins were unhaired using sodium sulphide. It was noted that the crude protease achieved complete unhairing in 12 hours without the emission of any pungent smell. This was slightly longer than the period (7 hours) required to completely unhair test pieces at the laboratory scale. This can be attributed to the varying processing conditions, such as the temperature and the pH in the tannery processing drum. The novel protease from Bacillus cereus strain 1-p recorded a relatively shorter unhairing period compared to the ones reported from previous studies on alkaline proteases that reported unhairing periods of 16 hours up to 24 hours [13,14,22,44,45].

Visual examination of the pelts after the completion of the unhairing process showed that the pelt from the experimental group (enzyme-unhaired) was whiter and had a cleaner grain surface, void of hair follicles and epidermal structures, compared to the control group (sulphide-unhaired), which had darker patches, as displayed in Figure 4. This necessitated a further process step, bating of sulphide-unhaired pelts, the aim of which was to make the grain surface cleaner by removing scud and epidermal debris [46]. These results are in agreement with those reported by the previous research studies [8,13,47,48].

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(b)

(a)

Figure 4. Comparison between the enzyme-unhaired pelt (a) and the sulphide-unhaired pelt (b)

A significant amount of intact hair was recovered from the enzymatic unhairing system while the sulphide system produced hair that was turned into a sludge-like mass (pulped form) with no distinctive structure.

The hair was easily sieved out of the unhairing liquor, thus reducing the solid waste in the resultant effluent stream. Similar observations have been reported from previous enzymatic unhairing studies, whereby undamaged hair was recovered, which translated to the overall reduction of the pollution load in the wastewater [13,48-50].

Both groups of unhaired pelts were further processed, tanned into wet-blue and post-tanned into crust leather as displayed in Figure 5. The physical properties of the experimental and control groups were tested and compared.

a) Raw wet-salted goatskins

b) Wet-blue goatskin leather

c) Crust goatskin leather

Figure 5. Enzymatically processed goatskin from the raw stage (a), through wet-blue (b) to crust stage (c)

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Organoleptic and physical properties of the resultant leather Physical properties of leather are vital quality parameters that determine the leather’s performance characteristics in various applications, while organoleptic features indicate the general appeal of leather. The overall properties of the enzyme-processed leathers were either similar or better compared to the sulphideprocessed leathers. Organoleptic properties of leather make the product unique and valuable for various applications.

Organoleptic properties The visual and hand assessment of the conventional and the enzyme-unhaired leathers by experienced leather technologists showed that the enzyme-unhaired leathers were comparable or marginally better in appearance, softness, fullness, colour intensity and uniformity as presented in Table 1. The enzyme-unhaired leathers generally showed superior properties in the assessed parameters with the following ratings: appearance (9.5), softness (9.5), fullness (9.2) and colour intensity and uniformity (9.6) compared to the conventionally processed leathers with the ratings: appearance (8.9), softness (8.5), fullness (8.8) and colour intensity and uniformity (9.2). It was also notable that wrinkles were more prevalent in the enzyme-unhaired group (rated 9.8) compared to the sulphide-unhaired group (rated 9.0).

Table 1. Visual and hand assessment of the conventional and the enzyme-unhaired leathers Appearance

Rating (out of 10)

Softness

Fullness

Wrinkles

Colour Intensity & Uniformity

Conv.

Enzy.

Conv.

Enzy.

Conv.

Enzy.

Conv.

Enzy.

Conv.

Enzy.

8.9

9.5

8.5

9.5

8.8

9.2

9.0

9.8

9.2

9.6

Where: Conv. – Conventional (sulphide) unhairing; Enzy. – Enzymatic unhairing

The enzyme-unhaired leather was of good quality characterized by uniform colour, smooth grain, appreciable flexibility and a good appearance without any scud. This general observation has been attributed to the enhanced uptake of processing chemicals following the sufficient opening up of the fibre matrix as documented by previous research on enzymatic unhairing that reported similar results [7,12,13,18,47].

The general appearance of the conventionally and enzymatically treated goatskin leathers had a clear and clean grain without any foreign materials, but the enzyme-unhaired leathers were rated higher for the smooth feel, the gloss of the grain surface, a good handle, colour evenness and the general fullness of the leather structure. This can also be attributed to the enhanced absorption of tanning chemicals following the adequate splitting of collagen fibres. Similar observations on the appearance and fullness of the enzymeunhaired leather have previously been reported [7]. The ‘fibres splitting’ effect of the enzyme processing also influences the uptake of colour and dye material, thus giving the leather the observed deeper and more uniform colour [14].

The average ratings on the softness of the leathers suggest that the enzymatically processed leathers were much softer than the sulphide-processed leathers. Enzymatically processed leathers have previously been reported to be softer due to the enzyme�s action on non-structural proteins [12, 51]. This implies that enzyme application softens leather and makes it more pliable to the feel and touch. Leather softness can be associated with the fibre opening up [52]. Besides fully opening up the collagen structure, it is reported that enzymatic unhairing degrades the elastin network as opposed to the lime-sulphide system [48]. The

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soft feel of the leather produced by the enzymatic unhairing process, therefore, can be explained by the removal of elastin, making it more flexible, supple and pliable. This is a desirable feature for the production of soft and pliable products like upholstery, garment and glove leathers. Similar observations on the enzyme-unhaired leathers being softer compared to the sulphide-unhaired ones have been reported [53].

The enzyme-unhaired leathers were also characterized by many wrinkles compared to the sulphide-unhaired leathers. The degradation of the elastin can also explain the evident prevalence of wrinkles in the enzymeprocessed leathers. Elastin is an important protein that enables the skin to resume its shape after stretching or contracting. Hence, after its degradation, the leather surface does not regain its shape after distortion.

Similar observations were made when an enzyme extract from Bacillus crolab MTCC 5468 was used to process goatskins [7].

Physical properties Table 2 shows the physical properties of the resultant crust leathers. The general outlook of the sulphideunhaired and the enzyme-unhaired leather was comparable. The physical properties of both groups of leather met the minimum recommended standards [54]. The leathers obtained from enzymatic unhairing showed comparable tensile strength, distension at grain crack and distension at grain burst values to sulphideunhaired leathers with no significant difference between them (p values 0.81, 0.489 and 0.147 respectively).

The elongation at break and tear strength values for the experimental leathers showed that there may be a significant difference when compared to the control samples (p values 0.026 and 0.037 respectively).

Table 2. Physical properties of the leathers from the enzymatically and the sulphide-unhaired goatskins Tensile Strength (N/mm2)

Elongation (%)

Tear Strength (N/mm)

Grain Distension (mm)

Grain Distension (mm)

↑

→

Mean

↑

→

Mean

↑

→

Mean

Crack

Burst

Conventional unhairing

33.01

16.87

24.94

64.79

70.46

67.63

40.16

42.70

41.43

7.79

8.01

Enzymatic unhairing

33.73

20.13

26.93

65.68

86.89

76.29

42.37

44.81

43.59

7.89

8.23

Where: → - Perpendicular to the backline (transverse); ↑ - Parallel to the backline (longitudinal)

The comparability of the physical properties can be attributed to the fact that both unhairing techniques preserve the collagen content without causing damage. These results show that the crude protease does not compromise the strength of the collagen structure and therefore the technique is effective and practically feasible. Additionally, these results correspond to the properties of enzymatically unhaired leathers previously described, showing comparable or superior physical properties when compared to sulphideunhaired leathers [13,47,48]. Notably, the grain distension resistance of the enzyme-unhaired leathers was better than that of the sulphide-unhaired leathers as presented in Table 2. This can be attributed to the fact that the enzyme action is less harsh to the grain layer compared to the sulphide action and also the enhanced absorption of tannins, which has been previously observed and reported in the enzymatically processed leathers [7,18].

Further observations were made concerning the sampling direction of the samples obtained for physical testing. Similar trends were observed in both the enzyme-unhaired and the sulphide-unhaired leathers concerning the sampling direction for tensile strength, percentage elongation and tear strength, as shown

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by the results in Table 2. The tests pieces sampled parallel to the backbone recorded higher tensile strength values (sulphide-unhaired: 33.01 N/mm2 and enzyme-unhaired: 33.73 N/mm2) than the perpendicularlysampled test pieces (sulphide-unhaired: 16.87 N/mm2 and enzyme-unhaired: 20.13 N/mm2). For the samples cut parallel to the backbone, most of their fibres are aligned in the same direction as the applied stress, hence having very little room to orientate towards the strain axis [55]. This means that the leather fibres themselves are strained, as there is minimal strain/stretch gained, as there is a minimal orientation of the fibres, explaining the higher tensile strength values. These conclusions are in agreement with those observed on the enzyme-unhaired leathers and the general behaviour of leathers during physical testing with regard to the sampling direction [13,56].

On the contrary, the samples cut perpendicularly to the backbone had higher percentage elongation and tear strength than those sampled parallel, as shown in the results in Table 2. The percentage elongation values (sulphide-unhaired: 64.79% and enzyme-unhaired: 65.68%) and the tear strength values (sulphideunhaired: 40.16 N/mm and enzyme-unhaired: 42.37 N/mm) of test pieces cut parallel to the backline were lower than the percentage elongation values (sulphide-unhaired: 70.46% and enzyme-unhaired: 86.89%) and tear strength values (sulphide-unhaired: 42.70 N/mm and enzyme-unhaired: 44.81 N/mm) of samples cut perpendicular to the backline. For the test pieces cut parallel to the backline, the fibre network is assumed to be naturally orientated to the same direction as the strain axis. In this case, the specific work of fracture was higher because the tear does not grow through the fibre diameters but instead propagates in a more straightforward rupturing process and hence the tear strength is low [56]. The percentage elongation is equally lower in these samples as the stress acts on the leather fibres themselves, which are strained with minimal stress. Similar findings concerning sampling direction when carrying out physical tests have been reported [48,55-57].

Pollution load in resultant wastewater Wastewaters from both unhairing techniques were assessed and the results are presented in Table 3. The results are expressed in parts per million (ppm).

Table 3. Pollution load in unhairing wastewater streams Enzymatic unhairing group

Sulphide unhairing group

Percentage reduction of pollution (%)

BOD

940

4 200

78

COD

3 200

19 200

83

TDS

12 800

50 400

75

TSS

1 300

3 460

62

44 litres

88 litres

50

Pollution loads (ppm)

Total wastewater volume from the unhairing process

The presence of organic matter in wastewater contributes to increased BOD, COD, TDS and TSS [7]. It is clear from the results that the enzymatic unhairing, using the crude protease from Bacillus cereus strain 1-p, leads to a significant reduction in BOD by 78%, COD by 83%, TDS by 75% and TSS by 62%. It was equally notable that the volume of the wastewater produced after the unhairing process was reduced by 50% in the enzymatic technique. The hair shafts were removed completely intact and recovered from the unhairing liquor; hence the wastewater was free from hair and epidermal matter unlike in the conventional technique. The significant reduction in the pollution load can be attributed to the complete elimination of sodium sulphide www.textile-leather.com 49

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which solubilizes the hair and epidermis during the unhairing. These findings agree with previous findings from enzymatic unhairing systems that reported that enzymes drastically shrink the effluent pollution load and help in hair recovery [25]. Similar results have been reported from proteolytic alkaline unhairing systems indicating a significant reduction of the pollution loads from the unhairing wastewater streams [7,14]. However, the pollution load reduction from the unhairing process using this novel protease recorded a higher reduction compared to that reported by Senthilvelan et al. (2012), with a 62.8% and 79.0% reduction in BOD and COD respectively. Hence, the protease extract from Bacillus cereus strain 1-p is a viable and potential alternative for cleaner leather production.

The overall cost of leather production to the crust stage after the unhairing using the crude protease was approximately 0.55 USD per square foot compared to the cost of the conventional processing which was approximately 0.49 USD per square foot. The cost of the enzymatic unhairing technique was estimated from an inclusive calculation of the costs of all the laboratory reagents used for the enzyme extraction together with the processing chemicals at the tannery. Despite the slightly higher cost of production, the enzyme technique significantly reduced the pollution load, which would reduce the cost of effluent treatment and thus, give it an edge over the conventional technique.

CONCLUSION This Bacillus cereus strain demonstrated the ability to secrete proteases that acted on the epidermal structure and hair, thus enabling their removal. The complete unhairing of the goatskins using the crude protease extract from Bacillus cereus strain 1-p took 12 hours at a relatively low temperature of 27°C. This unhairing technique yields leather that has comparable or even superior strength properties as well as organoleptic properties such as softness, fullness and colour uniformity when compared to the sulphide unhairing technique. The enzyme also facilitated the removal of the hair intact, which not only lowers the pollution load in the wastewater but also leads to recovery of the hair, which can be used for other industrial applications.

The novel crude alkaline protease enzyme from Bacillus cereus strain 1-p can, therefore, be used to make leather processing cleaner and sustainable by eliminating the use of sodium sulphide without compromising on the quality of the resultant leather, and should, therefore, be explored for industrial applications and commercialization.

Acknowledgments The authors wish to thank Bio-Innovate Africa for their financial support of this study. The authors acknowledge the Leather Industries of Kenya for their kind collaboration in the processing of samples for the study.

Special thanks to the University of Nairobi staff and colleagues from the Department of Public Health Pharmacology and Toxicology and the Department of Biochemistry.

REFERENCES [1] UNIDO. United Nations Industrial Development Organization, Vienna: Future Trends in the World Leather and Leather Products Industry and Trade [Internet]. 2010 [cited 2019 Nov 4]. Available from:https:// leatherpanel.org/sites/default/files/publications-attachments/future_trends_in_the_world_leather_ and_leather_products_industry_and_trade.pdf [2] Hansen ER, Moon Y, Mogollon MP. Kenya - Leather industry : diagnosis, strategy, and action plan [Internet]. The World Bank; 2015 Jun [cited 2019 Nov 4] p. 1–126. Report No.: 99485. Available from:http://documents.worldbank.org/curated/en/397331468001167011/Kenya-Leather-industrydiagnosis-strategy-and-action-plan 50 www.textile-leather.com

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[3] George N, Chauhan PS, Kumar V, Puri N, Gupta N. Approach to ecofriendly leather: characterization and application of an alkaline protease for chemical free dehairing of skins and hides at pilot scale.

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by Bacillus megaterium RRM2: application in detergent and dehairing industries. Journal of basic microbiology. 2011;51(6):614–624. https://doi.org/10.1002/jobm.201000517 [23] Saleem M, Rehman A, Yasmin R, Munir B. Biochemical analysis and investigation on the prospective applications of alkaline protease from a Bacillus cereus strain. Molecular biology reports. 2012;39(6):6399– 6408. https://doi.org/10.1007/s11033-011-1033-6 [24] Sundararajan S, Kannan CN, Chittibabu S. Alkaline protease from Bacillus cereus VITSN04: Potential application as a dehairing agent. Journal of bioscience and bioengineering. 2011;111(2):128–133. https:// doi.org/10.1016/j.jbiosc.2010.09.009 [25] Wanyonyi WC, Shiundu, Paul M., Onyari, John Mmari, Mulaa, Francis J. Isolation and characterization of biomass modifying enzymes for bioremediation and production of “green specialty products.” 2015.

[26] Mienda BS, Huyop F. Characterization of Bacillus cereus BM1 with protease activity. Research in Biotechnology. 2013;4(3). Available from: http://updatepublishing.com/journal/index.php/rib/article/ view/2430.

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[33] IULTCS/IUP 9. ISO 3379:2015 [IULTCS/IUP 9] Leather — Determination of distension and strength of surface (Ball burst method) [Internet]. ISO. 2015 [cited 2020 Feb 24]. Available from: https://www.iso. org/cms/render/live/en/sites/isoorg/contents/data/standard/06/38/63871.htm [34] Eaton AD, Clesceri LS, Rice EW, Greenberg AE, Franson MAH. Standard methods for the examination of water and wastewater . Washington, DC: American Public Health Association (APHA); American Water Works Association; Water Environment Federation. 1995.

[35] Li S. Chapter 11 - Fundamentals of Biochemical Reaction Engineering. In: Li S, editor. Reaction Engineering [Internet]. Boston: Butterworth-Heinemann; 2017. p. 491–539. Available from: http://www.sciencedirect. com/science/article/pii/B9780124104167000112 [36] Reece JB, Urry LA, Cain ML, Wasserman SA, Minorsky PV, Jackson RB. Campbell Biology (10th Edition) [Internet]. New York: Pearson; 2013 [cited 2020 Jan 7]. Available from: https://www.biblio.com/book/ campbell-biology-10th-edition-reece-jane/d/1290432081 [37] Deng A, Wu J, Zhang Y, Zhang G, Wen T. Purification and characterization of a surfactant-stable highalkaline protease from Bacillus sp. B001. Bioresource technology. 2010;101(18):7100–7106. https:// doi.org/10.1016/j.biortech.2010.03.130 [38] Dorra G, Ines K, Imen BS, Laurent C, Sana A, Olfa T, et al. Purification and characterization of a novel high molecular weight alkaline protease produced by an endophytic Bacillus halotolerans strain CT2.

International journal of biological macromolecules. 2018; 111:342–351. https://doi.org/10.1016/j. ijbiomac.2018.01.024 [39] Gao R, Shi T, Liu X, Zhao M, Cui H, Yuan L. Purification and characterisation of a salt-stable protease from the halophilic archaeon Halogranum rubrum. Journal of the Science of Food and Agriculture.

2017;97(5):1412–1419. https://doi.org/10.1002/jsfa.7879 [40] Jaouadi B, Abdelmalek B, Fodil D, Ferradji FZ, Rekik H, Zaraî N, et al. Purification and characterization of a thermostable keratinolytic serine alkaline proteinase from Streptomyces sp. strain AB1 with high stability in organic solvents. Bioresource technology. 2010;101(21):8361–8369. https://doi.org/10.1016/j. biortech.2010.05.066 [41] Daniel RM, Danson MJ. Temperature and the catalytic activity of enzymes: A fresh understanding. FEBS Letters [Internet]. 2013 [cited 2019 Nov 13]; 587(17):2738–43. Available from: https://febs.onlinelibrary. wiley.com/doi/abs/10.1016/j.febslet.2013.06.027 [42] Covington AD. Tanning Chemistry: The Science of Leather. Royal Society of Chemistry; 2011. 483 p.

[43] Sheikh J, Bramhecha I. 6 - Enzymes for green chemical processing of cotton. In: Shahid-ul-Islam, Butola BS, editors. The Impact and Prospects of Green Chemistry for Textile Technology [Internet]. Woodhead Publishing; 2019 [cited 2019 Nov 14]. p. 135–60. (The Textile Institute Book Series). Available from: http://www.sciencedirect.com/science/article/pii/B978008102491100006X [44] Nagal S, Kango N, Jain PC. Production of alkaline protease from Elizabethkingia meningoseptica KB042 using chicken feathers. Annals of Microbiology [Internet]. 2010 Dec [cited 2020 Apr 23];60(4):629–35. https://doi.org/10.1007/s13213-010-0101-9 [45] Vijayaraghavan P, Lazarus S, Vincent SGP. De-hairing protease production by an isolated Bacillus cereus strain AT under solid-state fermentation using cow dung: Biosynthesis and properties. Saudi journal of biological sciences. 2014;21(1):27–34. https://doi.org/10.1016/j.sjbs.2013.04.010 [46] Santos LM, Gutterres M. Reusing of a hide waste for leather fatliquoring. Journal of Cleaner Production.

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Instructions for Authors TEXT LEATH REV 4 (1) 2021 55-58.

INSTRUCTIONS FOR AUTHORS EDITING YOUR MANUSCRIPT Please use our template to edit your article before submitting for review.

• Volume of a manuscript should not exceed 10.000 words, without Tables, Figures and Images.

• Title of a manuscript should not exceed 15 words.

• Full names and surnames of the authors, as well as full names of the author’s affiliation – university, institute, company, department, town and country should be clearly given. Corresponding author should be indicated, and their e-mail address provided.

• Abstract of a manuscript should be no longer than 250 words.

• Keywords should contain 3-7 items.

• SI units should be used throughout.

• Abbreviations should be used according to IUPAC and ISO standards and defined when first used.

• Footnotes should be avoided. When their use is absolutely necessary, they should be numbered consecutively using Arabic numerals and appended at the end of the manuscript.

• References should be cited using Arabic numbers in square brackets, according to the Vancouver referencing style. Please use our Quick Reference Guide (or look at the next page) • Figures and illustrations with a title and legend should be numbered consecutively (with Arabic numerals) and must be referred in the text. Images should be numbered as Figures. Additionally, Figures should be supplied as a separate file saved as jpg or tif at 300 dpi minimum. Type size in the description of axes should be proportional to the size of the Figure.

• Tables with a title and optional legend should be numbered consecutively and must be referred in the text.

• Acknowledgements may be included and should be placed after Conclusions and before References.

CATEGORIZATION OF ARTICLES Distinguishing scientific from professional articles The importance of usefulness of a article is not determined by whether it is scientific or professional. The difference between a scientific and a professional work is the originality of the results of research, debate and conclusions obtained by verified scientific methods. A professional paper can be more important for spreading knowledge and profession and economically more useful in application, but this does not mean it is a new contribution to the increase of scientific knowledge.

The received manuscripts are categorized into: Original scientific papers means it is the first publication of original research. It must be presented so that the research can be repeated giving results with equal precision within the limits of the trial error, which means that the correctness of analyses and conclusions can be checked.

Scientific review is a complete review of a issue or a field of research based on already published work but contains original analyses synthesis or suggestions for further research. It has a more comprehensive introduction than the original scientific paper.

Preliminary communication includes new scientific results demanding urgent publication while the research is underway. This kind of article does not have to ensure the repetition and checking the presented results.

It is published only with the author’s obligation to publish the original scientific paper when the research is completed.

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Conference paper is the work presented at a professional conference organized on local, regional or state level. It will be published if it has not been published in full in Proceedings, as a report, a study etc.

Professional paper deals with the issues in the profession. It gives professional instructions and suggestions for how to solve the issue (technique, technology, methodology).

Professional review is a complete review of a professional issue (technique, technology, methodology) based on already published work indicating the best ways for solving the issue.

The papers that are not categorized include: Presentation and communication from practical experience deals with solving the problem of particular laboratory, institution or industry and serve to inform interested parties of the solution applied.

Position paper is an essay that presents an arguable opinion about an issue.

Commentary is paper connected with actual news and condition in science and textile/clothing industry.

QUICK REFERENCE GUIDE Vancouver referencing style consists of: • citations to someone else’s work in the text, indicated by the use of a number, • a sequentially numbered reference list at the end of the document providing full details of the corresponding in-text reference.

In-text citations • Insert an in-text citation: o when your work has been influenced by someone else’s work, for example: ▪ when you directly quote someone else’s work ▪ when you paraphrase someone else’s work • General rules of in-text citation: o A number is allocated to a source in the order in which it is cited in the text. If the source is referred to again, the same number is used o Use Arabic numerals in square brackets [1], [2], [3], … o Superscripts can also be used rather than brackets o Reference numbers should be inserted to the left or inside of colons and semi-colons o Reference numbers are placed outside or after full stops and commas Multiple works by the same author: Each individual work by the same author, even if it is published in the same year, has its own reference number.

Citing secondary sources: A secondary source, or indirect citation, occurs when the ideas on one author are published in another author’s work, and you have not accessed or read the original piece of work. Cite the author of the work you have read and also include this source in your reference list.

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In-text citation examples The in-text citation is placed immediately after the text which refers to the source being cited: ...and are generally utilized as industrial textile composites.[1] Including page numbers with in-text citations: Page numbers are not usually included with the citation number. However should you wish to specify the page number of the source the page/s should be included in the following format: …and are generally utilized as industrial textile composites.[1 p23] Hearle [1 p16-18] has argued that...

Citing more than one reference at a time: The preferred method is to list each reference number separated by a comma, or by a dash for a sequence of consecutive numbers. There should be no spaces between commas or dashes For example: [1,5,6-8] Reference List • References are listed in numerical order, and in the same order in which they are cited in text. The reference list appears at the end of the paper • Begin your reference list on a new page and title it References • The reference list should include all and only those references you have cited in the text • Use Arabic numerals [1], [2], [3], …

• Full journal titles are prefered • Check the reference details against the actual source - you are indicating that you have read a source when you cite it Scholarly journal articles • Enter author’s surname followed by no more than 2 initials (full stop) • If more than 1 author: give all authors’ names and separate each by a comma and a space • For articles with 1 to 6 authors, list all authors. For articles with more than 6 authors, list the first 6 authors then add ‘et al.’

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• Page numbers, eg: 123-129.

Digital Object Identification (DOI) and URLs The digital object identifier (DOI) should be provided in the reference where it is available.

Use the form as it appears in your source.

Print journal article – Ferri L de, Lorenzi A, Carcano E, Draghi L. Silk fabrics modification by sol-gel method.

Textile Research Journal. 2018 Jan;88(1):99-107.

▪ Author AA, Author BB, Author CC, Author DD. Title of article. Title of journal. Date of publication YYYY Mon DD;volume number(issue number):page numbers.

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Electronic journal article – Niculescu O, Deselnicu DC, Georgescu M, Nituica M. Finishing product for improving antifugal properties of leather. Leather and Footwear Journal [Internet]. 2017 [cited 2017 Apr 22];17(1):31-38. Available from: http://revistapielarieincaltaminte.ro/revistapielarieincaltaminteresurse/en/ fisiere/full/vol17 -nr1/article4_vol17_issue1.pdf ▪ Author AA, Author BB. Title of article. Title of Journal [Internet]. Date of publication YYYY MM [cited YYYY Mon DD];volume number(issue number):page numbers. Available from: URL Book – Hu J. Structure and mechanics of woven fabrics. Cambridge: Woodhead Publishing Ltd; 2004. 61 p.

▪ Author AA. Title of book. # edition [if not first]. Place of Publication: Publisher; Year of publication.

Pagination.

Edited book - Sun G, editor. Antimicrobial Textiles. Duxford: Woodhead Publishing is an imprint of Elsevier; 2016. 99 p.

▪ Editor AA, Editor BB, editors. Title of book. # edition[if not first]. Place of Publication: Publisher; Year.

Pagination.

Chapter in a book - Luximon A, editor. Handbook of Footwear Design and Manufacture. Cambridge: Woodhead Publishing Limited; 2013. Chapter 5, Foot problems and their implications for footwear design; p.

[90-114].

▪ Author AA, Author BB. Title of book. # edition. Place of Publication: Publisher; Year of publication.

Chapter number, Chapter title; p. [page numbers of chapter].

Electronic book – Strasser J. Bangladesh’s Leather Industry: Local Production Networks in the Global Economy [Internet]. s.l.: Springer International Publishing; 2015 [cited 2017 Feb 07]. 96 p. Available from: https://link. springer.com/book/10.1007%2F978-3-319-22548-7 ▪ Author AA. Title of web page [Internet]. Place of Publication: Sponsor of Website/Publisher; Year published [cited YYYY Mon DD]. Number of pages. Available from: URL DOI: (if available) Conference paper – Ferreira NG, Nobrega LCO, Held MSB. The need of Fashion Accessories. In: Mijović B. editor. Innovative textile for high future demands. Proceedings 12th World Textile Conference AUTEX; 13-15 June 2012; Zadar, Croatia. Zagreb: Faculty of Textile Technology, University of Zagreb; 2012. p. 1253-1257.

▪ Author AA. Title of paper. In: Editor AA, editor. Title of book. Proceedings of the Title of the Conference; Date of conference; Place of Conference. Place of publication: Publisher’s name; Year of Publication. p. page numbers.

Thesis/dissertation – Sujeevini J. Studies on the hydro-thermal and viscoelastic properties of leather [dissertation]. Leicester: University of Leicester; 2004. 144 p.

▪ Author AA. Title of thesis [dissertation]. Place of publication: Publisher; Year. Number of pages Electronic thesis/dissertation – Covington AD. Studies in leather science [dissertation on the internet].

Northampton: University of Northampton; 2010. [cited 2017 Jan 09]. Available from: http://ethos.bl.uk/ OrderDetails.do?uin=uk.bl.ethos.579666 ▪ Author AA. Title of thesis [dissertation on the Internet]. Place of publication: Publisher; Year. [cited YYYY abb. month DD]. Available from: URL This quick reference guide is based on Citing Medicine: The NLM Style Guide for Authors, Editors, and Publishers (2nd edition). Please consult this source directly for additional information or examples.

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